Hello dafreak, if you tape about:crashes in your URL bar, do you have crash reports stored you can with us?

the browser couldnt even start, how can I do that?

You could try uninstalling Firefox. Profiles/bookmarks/passwords should be left and install a full version Firefox 56.0.1 https://www.mozilla.org/en-US/firefox/all/

Suggest saving before doing the above. https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Do note that your Profile could be the cause of the issue.

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

dafreak said

Clean installed, removed every mozilla firefox folder from users, and it still doesnt work.

Have noticed that Win 7 is not getting the support that is needed for it like XP did when 7 came out. They are trying to migrate people to Win 10 as per stuff in tech sites. With that said you have do not send info to us un-ticked so no idea what Extensions you are using if any. So no idea about that. We have found that we are moving a lot of Win7 users to the Extended Version Release and people are happy with that and it is secure. You may wish to try that. https://www.mozilla.org/en-US/firefox/organizations/

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