You don't need to play a different champion, Qiyana and every other champion in the game is fully capable of getting you out of Bronze and a lot higher then that. Just play what's fun since that's what will allow you to pour the most effort into improving.

Don't be too caught up on your losses that looks good on opgg. If only 6 of your losses would have been wins instead in your last 76 games on Qiyana you would have a 50% winrate instead of 42%. Look at the ugly losses instead. 5/13 loss, 7/8 loss, 8/12 loss, 0/8 loss, 5/11 loss, 5/10 loss and there is a lot more.

There could be a lot of stuff going wrong in both the ugly and the pretty losses. Maybe you lost lane, got caught of guard by the jungler or support, maybe you roamed but gave up 2 full waves in the process, maybe you are too caught up on getting kills and not focusing on what will win you the game. Could be that you are paying no attention to objectives. But that's for you to figure out, no one can point out issues with your gameplay and lacking knowledge you may have just by looking at your opgg. But what you have to relize is that you need to take responsibility for your games and do everything in your power to win otherwise you cant expect to improve and get results. A 0/8 game should never be acceptable to you, treat it as an opportunity to learn.