My main keywords lost ranking on google.

Hello everyone on BHW! I'm here again.
I lost my main keywords ranking last month. This is the inner page of my website.
But other ranking keywords on this page do not seem to be greatly affected, why?

I write quality content and got some backlinks for it. The main keyword ranked 10-12 on google. (Failed to improve ranking)
And then I stopped link building work. Keyword rankings plummeted and then disappeared at the end of August. No ranking until today.

I'm questioning whether I'm really fit for SEO.

lalapilipa said:

The main keyword ranked 10-12 on google. (Failed to improve ranking)

Click to expand...

If I understood you correctly, you were ranking well before and then got backlinks and updated the post to improve it more?