Need help hardstuck

I need help climbing out of d4-d3 I just cant seem to get anywhere. I just go to d3 down to d4 and stay at 50% winrate. Often time I lose because someone on the enemy team is a fucking raid boss 3 levels ahead their lane opponent. How do I deal with it what should I focus on to keep climbing? I dont seem to be improving at all since I just stay in the same elo day after day, what has helped you guys to keep improving? https://m.deeplol.gg/summoner?userName=Njunjes-EUW&region=EUW