Why when I have strengthened a topic several times and it has been recorded as 5/5 when I next log in the same topic has changed to 3/5 or 4/5? this keeps on happening so I cannot progress any further. NOT HAPPY!!!
Strengthening is totally optional, but I recommend it. But if they make you do it four times a day on a skill you already know, you really don't need to do it.
I'd say it's mostly that duolingo says a skill is gold when it really isn't. I find that now, even without much daily practice (maybe 1-2 strengthens a day most days), my French tree stays all gold everyday.
Just keep at it!