I'm playing my first D&D 5e character, a Wood Elf Fighter with the Soldier background. I have proficiency in the skills Acrobatics and Survival from the Fighter class, and Athletics and Intimidation from the Soldier background
I've just reached level 5, so my proficiency bonus increases from +2 to +3.
It makes sense that this bonus increase applies to my Fighter skills, since my level as a Fighter has increased, but do I also increase the proficiency in the two background skills?