I made a website with the kiki theme but am having problems with the homepage. For some reason I am not able to change the URL because a folder name can’t be added for this specific page. It is possible for any other pages. This is an issue because it is significantly lowering my google ranking. Would anyone know what to do about this?
All the page names should be index.html or index.php
And making the folder names repeat the root name is silly. Current https://www.pianolessons-london.co.uk/online_piano_lessons_london_nhs_offer/ should be https://www.pianolessons-london.co.uk/nhs_offer/
The previous version of your website had been in place since 2009. You probably built up several backlinks from other sites. That will give you a level of what Google calls authority.
That “authority” will help your SERP ranking a lot more than having multiple keywords in your URL. Especially if the keywords are duplicated in the same URL.
My bet is that your ranking dropped because when you redesigned the site and changed the URLs of each page you didn’t do any redirects from the old pages URLs to the new pages URLs. So you lost a lot of the old site’s SEO “juice”.
I would recommend setting up redirects from your old webpages to your new ones. This way Google will know that the SEO juice should be redirected to a new page. Make sure that the same content and meta tags are on the new pages so that you get all of the SEO benefits. I have some good live streams on SEO on my YouTube Channel