Re: Not coping with the new sensei
Leave, of course. Feel free to tell the sensei why on the way out.
But, the reason I'm suggesting you leave is that you mentioned twice that you don't consider the sensei very good. Whether they're not good, or its just your perspective, then you're wasting your time with them. Its going to get in the way of your training, and none of us have time to waste on bad practice.
(There's a whole lot of caveats and extra explanations I want to add on to that, but I'll leave it for now)