After a long break of play DnD my group wanted to start up a campaign again. We start making characters. My character is going to be an Elf that grew up as an orphan in this the large capital city thats in the world my DM is creating. My question is if my character is hundred/hundreds of years old wouldn't he know way more information on this city/ have more skills then a normal lvl 1? I just feel like my character would be at an advantage over other players.
Yes, being long-lived has its perks. Instead of thinking of it as an advantage over the other players, though, think of it as a party asset (unless you're playing in an adversarial game, in which case why do you care about having an advantage over everyone else?).
Your character's non-weapon proficiencies could reflect the aspect of their extremely long childhood that you want to take advantage of. Local History (Capital), Ancient Languages (Old Capitalese), Religion, Astrology, ... are all examples of skills you could take. Maybe your character spent 40 years begging/busking in the streets before picking up a sword/wand/harp, and thus knows some interesting figures in the capital's seedy underworld.
Write an extensive backstory, give your DM plenty of plot hooks that he can use to engage the party (and, let's be honest, to screw you over sometimes ;-) ). Leverage your character's age (perhaps you know where to find shelter when disaster strikes. Say you helped a human orphan when they were a fledgling and now, in their 60's, they can repay the favor).
There's always amnesia, though, or long stays in jail/forced labor. An orphan's life can be hard, and you may not have had the time or leisure to make friends and learn non-survival skills.
I'll start off by admitting that a case can be made for either side of the issue - you could argue that the elf should get more stuff, or point to the rules that say he wouldn't.
Personally, I think the right thing to argue is that the elf does not get extra stuff for being old, because it is more fair to the other players. With that in mind, we should make sure that the fluff side of things lines up with the rules that a 200 year old elf and a 20 year old human can both be level 1.
Elves are not human
Elves are elves. They see the world in an elfy way, act elvish, and value elvish things. Indeed, in mythology elves are fey, and not of this world at all! Given this, you could say - elves have a flighty attitude, and rarely focus long enough to master a skill. So while the elf could frequently mention that he used to be an apprentice blacksmith or was really into reading legal documents a few decades ago, he was never invested enough to learn very much, nor retain the little that he did learn.
An elf could spend some time in the city, then go to the countryside for a bit, maybe take a trip to the next city just because. Taking a sabbatical to hang out and meditate in the forest for a month? Super elfy, doesn't help you learn a lot of skills.
The skills the elf does learn, he does not necessarily push and perfect. Elves are deeply traditionalist, after all. Who needs these newfangled ideas when what he learned 50 years ago still works? He could be very skilled in an old, obsolete way of doing something, which is useless for actual adventure or application. Maybe he trained as a trumpet shiner, and then the trumpet shining market dried up after a Rust Monster plague destroyed them.
Cities are not dungeons
Adventurers rapidly gain levels because they put their lives on the line. Imagine your morning commute, but instead of potholes, the road had deadly pit traps, and instead of hobos, the bus contains a hobgoblin war party. When your boss asks you to take some documents down to the archive room, you have to strap on greaves and a breastplate to protect yourself from dire rats.
It is very likely that your elf does not do this. He wakes up, goes to work, does some boring task like shoe shining or cashiering or chimney sweeping or whatever it is most people do in your setting. Then he goes to the bar or home to do chores. Then he goes to sleep. His life is stable, and neither requires nor presents opportunities for improving himself and trying new things.
In his spare time, perhaps the elf trains as a wizard/fighter/rogue/whatever at the local mages guild/arena/criminal enterprise/other place. This is how he comes by the skills he starts the game with - a combination of his daily life skills and his part-time training in a profession useful to adventurers.
The short answer is, it shouldn't, especially out of fairness towards the other players.
The long answer: The main way a Character gains skill and proficiency is by using said skills in practice and dedicating themselves to said practice. Age by itself helps little. Take for example normal people in contrast to, for example, the people who are masters at playing the piano by the age of 18 (yes there are 5 year olds that are as skilled but im generalizing here). These individuals did not master their craft just because they are talented. They master it through hard work and dedication.
Just in the same way a level one character, while already more skilled than the average person, is still at the start of mastering their craft.
Another reason for this can be, for example, that dwarves, elves and other such long lived races have a very different perception of time. They accept that, for example by dwarfs a smiths apprentaceship may take 50+ years in certain systems. This means that they gather expierience at a different rate, but have a higher "skill cap" due to simply having more time available and better mastering the fundementals. The result is often that, especially for elves, they have a much more "spiritual" way of looking at their craft (for example elven rangers with their bow and arrows). They slowly become one with their weapon instead of seeing it as a tool.
In general I would advise that your level one character is not special. No matter the age he should not have any grand accomplishments, though a greater general knowledge in CERTAIN AREAS should be addmitted by the gm (for you that could example be either more extensive city knowledge or knowledge about certain groups within the city), but he should not be more skilled than the other characters. (especially since from an meta standpoint it would diminish the value of the other players)
For your special case, I would ask myself, how did my character survive for a hundred years in this city. Why hasen't he become more skilled? Is there some reason that he didn't have enough drive up until now, or maybe he was so busy just scraping by, being suppressed by other forces within the city. (just spitballing here though).