My Firefox keeps freezing for 2 Seconds after starting a download or uploading files. I have reinstallt it once now. I use the following Addons: (Picture)
What security software do you have? It is possible that (anti-virus) security software is causing the problem. Try to disable security software temporarily to see if that makes a difference.
If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, DuckDuckGo PE, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content.
- make sure your extensions and filters are updated to the latest version
This could be a problem with the places.sqlite and favicons.sqlite files in the Firefox profile folder.
- use the "Places Database" -> "Verify Integrity" button on the "Help -> More Troubleshooting Information" (about:support) page
If errors are reported with "Verify Integrity", close and restart Firefox or reboot and retry.