Welcome, @Miquel_R
Galaxy can import any data with a public URL link. This means not password protected but API keys can be involved.
Using the Google API should work. This would allow you to load files from your drive account – you can set the permissions to public sharing (anyone with a link). So, two steps but a potential solution that doesn’t involve a download. Splitting the files up into smaller chunks might be needed (what you seem to already be doing).
- Method was posted here by another user → Uploading data from google drive - #3 by vojtace
Other options involve setting up authentication inside your Galaxy account. Dropbox is one choice.
And this utility can be helpful for batch data loading from inside of an environment where the data is hosted.
I’ve cross-posted this over to the Admin chat to see if there is more advice. If you could confirm that you are working at the UseGalaxy.eu public server that might be relevant.
Hope this helps! 
Note: If you posted anything sensitive (I wasn’t sure?), you should update those credentials immediately since they were exposed publicly here.