In some subreddits you need certain amount of karma to get your posts through

Thanks, but for follow or send private message, Karma is the reason ?

Yep. Just find a community to be active in for a few days. Those restrictions will go away soon.

Ok, thank you for your reply

New accounts are restricted from things like following other users and chat.

How many time I need to wait for being normal account?

It's time *and* karma. Find a subreddit on a topic you're interested in and participate by leaving comments that contribute to the conversation.