Beginner here. Need help please

So a few days ago I bought some Bitcoin on cash app and tried to transfer to a marketplace to put in my wallet on the site. First time doing this so bear with me guys... Lol.
So I sent to the marketplaces BTC address. I was not aware I needed to have my own wallet first. I guess I needed to send it there before the marketplaces address first. So I was talking to a guy helping me out and was not able to get the coin I mistakenly sent into my new wallet. He said I needed to have something in my wallet first. So this morning I bought some coin from cash app again and was able to successfully send it to my new wallet. But IDK what happened, it was then withdrawn and sent somewhere shortly after I transferred to my wallet .. he again was helping me out telling me what to do but unfortunately I was lost at what he was trying to tell me to do. Just like I'm sure most people are lost at me trying to explain my situation here... Lol . So my question is can someone try to help an idiot out retrieve his coin? The plan was to put a little bit in my wallet so I could have retrieved my coin that is in limbo somewhere... I'm financially strapped at the moment so I kinda really need to get this back. If this makes sense to anyone and you can walk me thru what to do I would greatly appreciate it. Thanks so much