@heiheihei333 I believe what @Joker explained works the same for everyone by default, not something that was done for one individual member.
If you're facing a similar issue - being unable to download new torrents because you have no download slots available - it may be worth double checking things are as you think they are.
For example, are you aware there's a daily download limit? This varies member-to-member based on a combination of things like your ratio, whether you've donated recently, how many new torrents you've uploaded, and how many you're seeding. I don't recall what it is, but it's pretty high. I don't think I've ever hit mine, and there have been times when I've downloaded an awful lot in one day.
If you know that's not the cause, and you believe you're not subject to any bad ratio restriction, try pausing all those partially downloaded torrents where you've grabbed what you want, so only those that are active right now are still running. Give it an hour, then see if you can download new stuff. If it then works, you can restart your paused torrents - I'd suggest in small batches - and see if the problem has been cured or if it returns. If it does, you can at least then give a lot more information about your own situation which should help identify where the problem might lie in your particular case.