I’m struggling. Please help

Hi, I’m very new to the whole soldering world. I’ve watched plenty of tutorials and such online. However I’m really struggling with a few things.

I can’t seem to clean my tip. It just keeps oxidising and I don’t know how to clear it up. A sponge isn’t working. And I’m trying to desolder a through hole connector. But I can’t seem to get it to melt and suck away. The blob keeps getting bigger 😢

Any advice? I’ve tried more flux and such. Just doesn’t seem to work. I’m gonna guess this is a super simple fix I just don’t have the knack yet