Going on a dating app to get a boost in your self confidence is the exact opposite thing to do. Get the fuck off dating apps. Introspect about why you don't like yourself.
What you're doing wrong is using a dating app. Just don't. Not only are you unlikely to find a long term partner on a dating app, but it'll push you down the mindset you are already in of being fixated on dating someone.
You will not be happy once you have a girlfriend. Whatever void you are wishing to fill will not be filled.
Work on understanding your mind, on becoming more self aware. Develop as a person. Friendships and relationships are natural consequences to the act of being human.
If you're afraid of never getting a partner, look into that fear. Ask yourself why you are afraid. Is it because you don't think you have value as a person? Investigate that belief of why you don't value yourself. Whatever you find in your mind, look directly at it. It's your mind, it's all you've got, and it's not going anywhere.
I can guarantee you you will never find a partner by asking yourself "how can I get better at dating?" or "why won't she go out with me?" Just one look at the incel movement should tell you that that mindset is an antipattern. You are asking the wrong questions.
If you're afraid of introspecting on your mind, that should tell you just how desperately you need to take a good long look at it and see what's there.