I consider this project to be bad. there are no animations in the graphics at all, and it is not bad only in cut-scenes and the game is as simple as possible, you just go ahead

how big can be my team or i must work at single?

can I use unity or gotot or anything else?

good time killer

sound track is very simple and dialogues is quite bad, jump puzzles hard  is not mines but track resets every time you die and is very annoying, you need or make longer  puzzles or by codding make track unresetable. But  it's  not bad for one  developer  especially if thes first work.