This is the first time here, and I need your opnion in what version should I starting 4 or 5 ?
If you want to actually make games, 4.
5 is still very much in beta, it doesn’t have an expression editor yet, so you’d have to look up (if you find a reference) or ask someone about how to query certain values via code instead of using the drag and drop interface.
A lot of stuff is still missing in 5, but it is very promising, you should keep an eye out for it.
Apparently, there is the option to export your project as JSON, which can be used by both editors, so if you want to switch later, it should be possible from what I’ve read on these forums.