3 bet bigger preflop (I'm kind of confused as to what stakes this even is). Once you get led into I think you probably want to call here. It seems unlikely that villain is donk-getting it in with a hand like 99 so raising likely puts you up against a range of KJ+ and big draws. Furthermore, due to the small 3 bet sizing, stacking off with your hand on the flop becomes less appealing because you're fighting over less money. 

converter messed a little bit. He opened 4.75 i 3bet to 12. Confused too because almost noone opens for that amount pre. So should have raised to 14. But normally i 3bet 2.5x IP
As postflop i now think the best way is to call down unless spade hit.  

this hand...

pre i think calling is better its not like he calls worse hands often and when u face 4bet also not good. its better to 3bet polarized bb vs sb

Preflop reraise with KJo is a good adjustment to people who open for small amount from the SB with too loose of a range.  I'm assuming this guy is one of those people.  You'll want to 3-bet an insanely wide range vs a player like that so KJo ends up being straight value.  Flop looks fine.  You have a vulnerable hand and no backdoors so I'm happy to make this a big pot right away vs his fishy line.