a little help please

Try restarting steam.

After installing, you could verify files?

Try verifying the game cache. Right click on the game, click properties at the bottom, go to local files, then click on verify the game cache. That will allow Steam to check if you have the files and will download the ones you are missing.

Right click on warframe, press properties, press local files, press verify integrity of game cache. This allows steam to scan over your files and see if anything is missing. If anything IS missing, steam will re-install that file.
I think.
Edit: try the uninstall and reinstall method?

Look, I appreciate all the help I can get. Thanks for all the replies ^^

Edit: though I still need help

If the game isn't installed on C:/, maybe try installing and launching it there?

Looks like its time to contact support...

Hey, I got it working! Thanks for your support ^^ closing this thread now