There are many things of great importance when moving a shop such as you did. Firstly, make sure ALL versions are redirected and that the header response is a 301 redirect. So

http://www.domain.com
https://www.domain.com
http://domain.com
https://domain.com

Here is a tool to test https://www.internetmarketingninjas.com/header-checker/

Next it is important to understand that reindexing takes time and as much as Google denies as sandboxing period, it is none the less true. The period of time it takes to see a positive SERP change depends a great deal on the health of the site. I have seen sites with issues such as widespread duplicate content take a year or better to begin to show positive results.

Lastly, and the real bummer of the day is decay. This is a sad fact that through redirect, no matter how long or how healthy the site, some rank will be lost in the changeover.

Best advice is hang tough, create new, unique content every week and share pages (not spamming) on social media. If you have the skills a few easy pages with "link bait" which is content users find useful enough to share will help.

~Melanie