You forgot to mention following steps 
go to settings, then click on sync option
over there, click on start a new sync chain. it will provide you a 24 word code.
Nope I don't want to sync with cloud so better I will lose my data but I won't sync.
no no it will not save in cloud
So where will it save
Your data is already saved in their cloud or your own device, which on entering the 24 word code, will back up automatically.
Done reinstalling however I backed up that folder but only bookmarks are back IDK why but I am OK, and after reinstalling nothing fixed.
Can I try installing from software store once?
Try installing from snap. Yes software store. install it from there
No snap one also same problem.
I get this but all the things are broken too much broken 
What an annoying bug, isn't it 
Yes it is too much annoying only with brave now i am gonna report it on github.
ah wait, click on use classic button and send screenshot
when I click on classic it just same then brave does that trick that it does in normal version the upper buttons are not matched and however dark mode seems to working.
This is one of the last ways I have to fix this issue. click on additional settings and then click reset settings, then click restore settings to their default. this will not delete your data. Sorry in advance if it did delete your data 
But it doesn't works 
