How to change binds in vim?

Question

linux

Hello, I recently decided to switch to vim, before that I used sublime in Vintage Mode for about half a year, so editing the text itself does not cause problems, but there are small bugs with this mode, and I want somehow more old school.
Everything seems to be fine, but I can not solve a couple of problems:
1. How to change the button to enter the command (normal) mode? (on df keys) ?
2. How to switch tabs, close, etc. (:gT and just gt somehow don't work, most likely I read it crookedly (from English) and now I'm lamer) ?
3. And how to change the focus, i.e. so that the cursor is either in the sidebar (NERDTree) or in the window itself with the file being edited?

Answer 1

1) Any buttons and combinations can be set http://vim.wikia.com/wiki/..
3) NERDTree opens in its own window (in Wim terminology). Switching between windows is done via Ctrl + w + h/l/j/k.
I advise you to go through vimtutor , such questions will disappear.