Did you check your Option settings to see what it is set at?

Yes I did. The option setting is set to ask me every time I want to download something and where I want to save it. Firefox doesn´t even open PDFs in a new tab.

Hi, no idea. Sometimes a file gets corrupted or clipped and in updates maybe packet loss in the download.

Please give this a try : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 59.0 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

Hello,

thank you all for your help, but I solved the problem by coincidence.

In the description for "Information for Troubleshooting" I found the button "Clean Up Firefox" and after I've clicked on it the problem was gone :).

So I´m happy now :D.

Have a nice day.

Please Mark Your Answer as the Solution please to close this and so others can find it, or do not reply. Thank You.

Done :).