Please, tell me if I go through the game properly, at the end of the game what percentage of all skills and branches i will be able to learn? (I mean if game makes us choose certain branch or let's develop all?) And what max skillpoints is there?

thanks <3

Marcin Momot confirmed via Twitter that there is no level cap, so theoretically you could develop all of the skills, though I shudder to think how long that would take. With this information, some people have been asking for a new game plus mode, which would be kind of cool.

Source: https://twitter.com/Marcin360/status/600953392954011649

Once I've beaten the game I'll probably look for a mod to activate all already developed abilities instead of just having 12 you can "equip" because I want to be a super witcher.

I finished the game around level 35 myself...

I've seen a mod floating around the nexus that has a new game plus mode if you want to continue to level your current Geralt. Might be worth a look :)

As of June 2015, you can get around 55 skill points in total adding points for level advancement and places of power.

Where did you find this?

I calculated the skill points based on having found 21 places of power and I think I know where at least 2 others are.
Using the 21 places I found plus assuming you can reach level 35 (34 skill points) I came up with 55.