PvP combat does not have to be a bad thing. I have run and played in many games where various forms of PvP have been enjoyable and interesting, and did not lead to the problems you are facing.
The issue in your case sounds mostly about rules questions, rules lawyers, and the lack of a solid authority on the rules. Adding competitive players and PvP to that mix makes a recipe for upsets.
So address those things.
Unless none of the players care about exact rules (which is the opposite of your players), a game needs someone (preferably the GM) who is the authority on rules details, and who is accepted by everyone as the first and last ruler on what happens in the game, and what the rules are. Note those are two different but related things:
In most traditional RPGs, the GM should be clearly accepted by all players as the person who has the final say on what actually happens in play, regardless of the rules.
What the rules are, is different from GM rulings about what happens in the game world (perhaps in spite of the rules, see 1a, sometimes also called "rule zero"). It helps if the GM, or perhaps one or two other players have really mastered the rules, but if there is any disagreement about what the rules are, or who really understands them, in order for play to go smoothly in the case of disagreements, I recommend there be an agreed authority (typically the GM) to answer rules questions during play. The rules authority may hear an argument during play, but can also call for points about the rules to be held until after play is over, and his rules trump any arguments during play, except from the GM. So you all agree that the GM or an agreed expert gets to say what the rules are during play, and arguments about them are overruled by that person. If the PC of the rules expert is fighting another PC, it's best if you have another expert be the authority for that contest, if possible.
If you guys really care about the rules so much, and want to be able to do PvP combat smoothly, master the rules better and agree on them. One way to do this is to play a number of throw-away arena combats that aren't part of a campaign game world, or involve non-PC situations played out for fun, so there are no high stakes and you agree to find the rules edges and figure them out.
Since you're using translated foreign rules and no one really knows or agrees on all the rules, it could help to write your own house rules / interpretation of the rules, in English. Whenever a question or disagreement comes up, work out what the rules will be and write them down. This can be really helpful for many games that have rules holes, or where the group isn't happy with the rules in specific places.
In addition to addressing the issues with your group, for PvP in any group, I think it's very important to be careful about same page issues. Make sure that there is agreement about what sort of PvP is ok, or not, and what the procedure for it is. Some players don't want any non-cooperation between PCs. Some players hate their character to get hurt, embarrassed, or to lose any of their possessions. Some players will get into "betray the party" mode. Some players enjoy fighting other PCs, but some want to limit it to non-lethal blows, while others don't. Some players and some PCs hold grudges. Some players don't mind fighting other PCs, but expect to not actually be killed or maimed. All these sorts of expectations and potential upsets should be discussed, and it helps to try to make sure players are on the same page before each PvP situation happens, too.
Some of these distinctions can be helped by developing them as customs and laws and code of honor in the game world itself. Such as laws for fighting and duels, specifying what techniques can be used, when the fight is over, what the consequences of a fight are, and so on. (Hopefully your players won't also want to rules lawyer those, too... or will at least enjoy themselves when the do so.)