If you are a free user, do not try to download multiple files at once. Start one download, let it finish, and then start the next. Trying to start a second download will usually error out the first one. Set your downloads for overnight when you don't need your internet speed for other things.
If you have a massive file to download (e.g., a 50GB high-res texture pack), it may be worth paying for a single month of Pro or buying a "Download Pass" (if available for that specific file). This supports the file host and ensures you get the file quickly and safely. uploadhaven pro for free high quality
The free version is known for invasive pop-ups and potential malware redirects; Pro eliminates these ads entirely. If you are a free user, do not