I get a 3-bet from blind and call with AJs.
Flop is pair + FD, he checks i bet half pot, he called.
At this point i guess he has a weak A or a monster or like KK.
I dont bet the turn, should i ?
I think if i bet, he often folds and sometimes he has a draw too and we both hit on river a

PokerStars - $0.25 NL FAST (6 max) - Holdem - 6 players
Hand converted by PokerTracker 4

Hero (BTN): 108.56 BB
SB: 100 BB (VPIP: 16.97, PFR: 13.38, 3Bet Preflop: 3.81, Hands: 1,683)
BB: 146.16 BB (VPIP: 18.18, PFR: 9.09, 3Bet Preflop: 0.00, Hands: 11)
UTG: 103.64 BB (VPIP: 14.91, PFR: 10.53, 3Bet Preflop: 4.88, Hands: 122)
MP: 205.68 BB (VPIP: 19.59, PFR: 16.28, 3Bet Preflop: 4.01, Hands: 894)
CO: 245.64 BB (VPIP: 11.36, PFR: 7.95, 3Bet Preflop: 4.88, Hands: 91)

SB posts SB 0.4 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.4 BB) Hero has J A

fold, fold, fold, Hero raises to 2 BB, SB raises to 7.4 BB, fold, Hero calls 5.4 BB

Flop: (15.8 BB, 2 players) 7 A 9
SB checks, Hero bets 7.52 BB, SB calls 7.52 BB

Turn: (30.84 BB, 2 players) 3
SB checks, Hero checks

River: (30.84 BB, 2 players) T
SB checks, Hero bets 22.08 BB, SB calls 22.08 BB

Why are checking back turn? I would bet like2/3 of pot and if the river isn't a spade than i would probably check back. But i think you miss some value by checking back turn.

Could be, but he could also fold to a turnbet and call a riverbet and sometimes he c/r me with like 77,99.

Most of the time he will x/r you OTF with 77/99 and I doubt that he 3b 77/99 with ~4% 3b.

Ez bet OTT 1/2-2/3.

bet turn

If you want to pot control by only betting 2 streets.
Then bet the turn when you have wild equity. Then check the river if the flush bricks.

I'd check the flop if anywhere.

People XR flop if they have 2 pair+ and are X at 25nl fast. They don't XC these flops with made hands.

Turn is an easy bet.