New user - user password not accepted in terminal

I’ve just installed Manjaro on my computer. Have not used any Linux OS before so am VERY green.
When installing I selected to have same passwrod for user and root account (later read that maybe this wasn’t a good idea). If I remember correctly I then ran one update which required my password - this worked fine (autoinstalled proprietary driver).
However since then when prompted for my password to install apps the terminal is saying that my password is incorrect (have tried to usual: no capslock, retyping several times).
I’ve tried looking through this forum and have found other people w similar issues but haven’t been able to follow the suggested instructions given (again, v green to terminal/linux).

If someone is able to help/point me to a beginner-friendly guide to solving this I’d be very grateful.
Many thanks, Sofia

Please rephrase your topic - with proper spelling - do not type as if it is text to your friend.