When you have more CS than your opponent and still lose trades

Please stop shitposting every time some new laxative pops into your brain.

The game isn't linear. Champions aren't homogenous. By your logic, if every champion in the game had 50 cs, every champion in the game should be 100% equal in power. That's not true at all.

Tristana with 50 CS>Ashe with 60 CS. Renekton with 50 CS > Gangplank with 60 CS

Etc. You're dealing with multiple problems.

1. Early game champions. Powerful early, fall off late.
2. Mistaking CS for items. CS only matters when you recall. A 200 CS renekton at 20 minutes is no more fed on items than a 5 CS Fiora if neither have gone back. Experience doesn't require last hit, so dont just look at flat CS.
3. Itemization. You spent 700g on two long swords. Great. Didn't have enough to finish dirk for 400 more. You had 1000g. He had 800g, bought a chain vest. 20 AD vs 40 armor. So even though CS (roughly 10-13 ahead) dictates you in the lead, he very clearly had the better stats.
4. Counters. I don't care if you're Singed with like 50 cs ahead of Teemo, you're not fighting him.
5. Mechanics. Might just be getting outplayed. You tried 3rd Q on someone as Riven, they flashed behind you and just had a spell come up and beat you. That wasn't gold talking, that was mechanical play.

If you're playing as ziggs and have more farm than their zed, don't 1v1 him, he has more damage in his kit early game than you do.

Or you used abilities poorly and didn't have the right items for your damage spike.