Tor works by proxying through (at least) 3 PCs before hitting the open web. The problem is that you’re trying to download big files which is not a use case for tor.
It’s specifically for browsing the web anonymously.
When I first starting using Tor in the mid aughts, I was using it to download movies and music. I remember talking with a security friend and he was like, "Bruh, what are you doing? That's not what Tor is for." and then launched into a 20 min rant about why I was misusing Tor and affecting other people using the service by what I was doing.
It was a good lesson and helped me realize what Tor should really be used for.
For a circuit to clearnet it's 3. Guard --> Middle --> Exit. For a onion service it's 6 and the connection is a bit more complicated [0]. The speed varies from very fast to unbearable depending on your circuit and how bad the ddos is at that moment. [1] You can try to create a new and hopefully faster circuit by clicking on the onion symbol on the left in the address bar.
It was a good lesson and helped me realize what Tor should really be used for.