Are Google rankings affected when you switch servers?

Are Google rankings affected when you switch servers?

I recently moved from shared hosting to VPS, and I think traffic has decreased little since.
Is this normal, when you change server, Google will reduce your ranking?
If so, how long does it take to maintain the rankings?
SEMrush

In addition, what is the basic map of good SEO nowadays? Required return links, page referencing, etc.
Thank you