Google Search Console isn't re-indexing our website after url-structure-change.

We startet our new website in May 2021 with around 200 landing pages that google was indexing quite quickly without any problems. Then we changed our url-structure in July (around 2 month ago), submitted 20.000 new landing pages, and since then Google haven't really crawled / read us anymore, according to the Search Console...

Further infos:

• Google right now is indexing some of our old and some (really few) of our new urls - in total around 200 pages (of 20.000).
• The old ones of course are throwing errors... but will be redirected on our homepage.

Can anyone help how we can a) get rid of our old-url-structure landing pages from Google search results and b) how we can accelerate the crawling / reading process of our new landing pages??? Thanks in advance!!