No problem whatsoever.
He had 161 premier league games before the start of last season, when the best he'd ever managed was 11 goals. He was experienced then, and undeniably Sterling will continue to score. My argument he made massive improvements.
Mohamed Salah was 25 and had played 225 professional games before the start of last season, and he'd only managed more than 10 goals twice in 9 seasons. Then he hit 44 last year.
Lets not forget he scored more goals last season than in the previous 2 combined. He has already shown himself able to take massive strides in improving his goal scoring. Last year he really improved his finishing at the far post (the documentary mentioned Arteta coaching him to attack the ball, not just let it hit his foot) and now this season we seem to be seeing much more danger from around the edge of the box.
He still needs to work on 1v1's because he always wants to go around the keeper and lacks the confidence to finish past the keeper - but what we've seen so far makes me think he can definitely improve on those because he essentially just needs to do the same finish around the keeper he pulled off vs. Arsenal and Newcastle.
He will always miss chances because that's the kind of player he is, but Salah missed more big chances than anyone else in the league last year and scored 33 goals. Some of the misses he had were worse than anything Sterling pulls off but no one cares because he already had a huge number of goals that season. Sterling only needs to cut down on the misses a bit and he'll be hitting 30 goals a season, which is pretty much the gold standard for forwards.