NL2 AKo vs 3bet

You can 4 bet pre, your hand is strong enough.
We cannot call the turn.it is too expensive and there are only a few ways to win our money back.

4-bet/fold that pre-flop.
Calling puts you in a situation you never want to be.
1. His range is wide. He could be holding almost anything. You don't know where you are standing.
2. You are out of position.
My advice: try not to get in this type of situation, because you are going to make a lot of mistakes.

4betting sounds good. But can I start 4betting always my KK+, AK? And what if villain shoves do I call with AKo? I think folding AKo vs 3bet is out of question.

You should always be 4-betting KK+, AK out of position. A 5-bet almost always means AA in NL2, so you fold your AKo if he shoves. I don't think I've seen someone make a 5-bet with less than AKo in NL2. Best case scenario for you he is holding something with at least 40% to beat you.
Another advice: don't get too attached to AKo pre-flop. Don't get to attached too QQ+ postflop. Being able to lay these kind of hands is hard since you wait hundreds of hands to get them, but sometimes you know you are dominated and have to fold.

I think calling is much better than 4betting. IF you're going to 4bet, you can't fold to a shove... Otherwise why are you 4betting? You're hand is too strong to 4bet bluff with blockers, and 4bet/folding with a value hand and 100bb is pretty bad. However, AK isn't doing so great against an unknowns 5bet shove range. Therefore, I personally prefer a call at this level.

I'd also fold the flop, you're OOP with very little equity and some of your 6 overcard outs could very likely be dirty. (E.g. AQ, QQ, KQ, AA, KK)

You are 4betting because AK is strong but only preflop. After the cards are in the table is just another hand. You are out of position and you have no idea what villain might be holding. If you don't hit what do you do? I'd personally bet/fold it. If I get called I'm still not hitting I give it up. That's bad. If you hit you donk? He is probably going to fold if you donk. Not to mention if he sets something you lose your stack. Too many opportunities to make mistakes.

In my opinion you are giving too much value to AK. I'd rather play almost any hand at the button than AK out of position not being the pre-flop aggressor.

Simple plays -> less mistakes -> more money

Actually when I think about it calling the 3bet and donking flop might be the cheapest way to play that hand. If he calls our donk or raises it we pretty much know where we stand. In this case if we call and donk 1/2pot we have invested 0.4€. If we 4bet we have already invested over that and if he calls and the flop is that we are screwed. If we 4bet and cbet we have invested twice that amount and we get the same info about his range than with cold calling 3bet and donking.

Agree with lkdr9494, never fkat call 3bet with AK, even if you hit top pair top kicker you may not win if he horded AA

AK is Ana Kurnikova, looks good but never wins anyhing

The problem is that at NL2 villain can 3bet even AJo or weaker or middle pocket pairs (I have seen this). By calling we can play vs his weaker hands, we just have to be very careful. If we 4bet AK,KK+ always we get only folds or play vs KK+. That would also mean that we have to have a 4bet bluff range. I would start doing this at NL10 and above.

We need to 4b here, to make sure where we stand with our hand. Calling a 3b OOP will make you loose money calling, and hitting, wount extract that much value, and on a board Axx or Kxx you might get in a big trouble.

Actually when I think about it calling the 3bet and donking flop might be the cheapest way to play that hand

You don't have to think out side the box at NL5. You will come to the flop without initiative, which probablly worst case scenario 3b pot OOP without initiative, and donking.. for my eyes, you are representing only AQ, 33, 55, which probablly you wount be donking here, I would call you with big part of my range here.

As played I would c/c flop, c/f turn.

The main thing is we want to play this hand with initiative when OOP in a 3 B pot.