Weird download behaviour on steam

Had that problem, my friend told me it's like you got additional files or something that confuses steam and they are trying to fix it,
now I do not know if that is 100% true.

Sounds pretty legit though :d

Just change Download Region inside steam client; sometimes dl servers in some countries suck.

I had this problem yesterday, I fixed it by changing my region download from Argentina to Chile.
Steam >>> Settings >>> Download >>> Download Region

Did you try to clear download cache?
https://support.steampowered.com/kb_article.php?ref=3134-TIAL-4638

Have you restarted client, or if that failed, your computer? Restarting usually fixes Steam bugs, assuming they're not ones you just have to let time out or wait on fixes for. If you think it's on your end, you can right click on the game in question, and do a file integrity check, and see if that fixes anything [though I actually once had a FIC break a game entirely, forcing a reinstall o.O;].

Regardless of if it's an update or a first-time download, try downloading something else to give you a frame of contrast [as to if the issue is related to the particular download or not].

Clear the download cache and change the download region (and restart client/pc, of course)

i had this problem some days ago, it was only in that day though. Must be some kind of problem with the steam servers.

Have this same issue from time to time, though it's only for some games and not others more often then with all of them. Go figure.

Are you using a proxy?

Try to change the hard disk you're downloading to

I had this problem two days ago and it was only happening for one specific game, it fixed itself after a couple of hours.