I'm having this same issue now as well.

I can´t level up my proficiencies, so my character is incomplete and i cant´t start the game. I guess thats basically the same problem?

Yeah thats the problem

You have to spend one point in the ability that increases proficencie max, called critical precision, then spend those points and volla, in vannila i think you already start with that point so you dont notice it

The one point wont ruin your build, in fact its very easy to get more skills by maxing your mutaion stat as the game goes on