I am a very new online player. Villain is new to this table. Hero has $70 and villain has $50.

OTTH

Folded around to hero in CO with A 3 and opens to $2. Only villain in BB calls.

Flop ($4.50): Q 6 2. Villain checks, hero bets $3 and villain calls.

Turn ($10.50): 9. Villain checks, hero bets $6 and villain calls.

River($22.50): J. Villain checks. Hero?

Smaller pre. 2.5x is standard from the CO. You're just trying to steal the blinds from late position usually. I don't mind going bigger at low stakes if it's appropriate. But A3 is not a particularly good hand.

Flop is bigger than it needs to be. 1/3 pot is making almost all the same hands fold. We're in a less awkward spot if we get raised.

Turn you could bet or check. One argument for checking is that a lot of his range already folded the flop - it's a difficult board to hit. There are some questions about what is actually folding the turn. Barreling is totally fine though.

River you check back and lose . A queen is simply not folding very often. Betting again is throwing away a lot of big blinds for nothing.

I would check on the river since your removal is pretty bad and there's a small but non-zero chance you actually have the best hand if your opponent has worse clubs. Both cards in your hand are cards you want your opponent to have since they're more likely to fold with those cards. I would often check this hand on earlier streets though since you want to have some flushes in your range when you check and a club hits, and this hand is one of your best flush draws to check with.

Hands that I would 3barrel are any of 43s, 54s, 53s, 78s not of clubs, depending on what you're opening pre, and if you don't have too many of them, your lower bricked flush draws.

Basically same feedback as floponce

Generally we want to pick an open raise size of 2.5 to 3x. 4x is too big.

Flop and turn seem fine.

As played I'd usually check river