SEO Expert - Google Search Console issues; reduce crawl bloat

We have migrated from Magento to Shopify and the handling of the SEO has been somewhat poor.

We have the following issues in Google Search console:
Not found (404) Website Failed 570082
Blocked by robots.txt Website Not Started 937743
Alternative page with proper canonical tag Website Not Started 89354
Page with redirect Website Not Started 68908
Duplicate without user-selected canonical Website Not Started 1992
Excluded by ‘noindex’ tag Website Not Started 1054
Server error (5xx) Website Not Started 30
Crawled - currently not indexed Google systems Not Started 1273070
Duplicate, Google chose different canonical than user Google systems Not Started 34
Discovered – currently not indexed Google systems Not Started 10

We are looking for someone to resolve these issues and reduce our crawl bloat so Google in only crawling the pages we want crawling. We want to ensure our robots.txt file is configured to prevent parameter based indexing and remove any pages from Google which are impacted negatively.

We are running in Shopify and need someone with experience of resolving this issue.