I would like to ask that If we are building 100+ quality backlinks per month for my website and 20 backlinks are deleting each month from 100 backlinks so It would be ok or it would affect my website ranking.
It really depends on the quality of those backlinks. If you are losing 20 links with very low page authority (PA), low domain authority (DA), and high spam score, you will not be affected much, if at all. You shouldn't worry about this case. However, if you are losing 20 links with high PA, or high DA especially, you might be affected considerably, and should work to keep these links or get new links with similar PA and DA scores.
Building 100+ quality backlinks per month is good for your website's ranking. However, losing 20 backlinks each month from the 100 built may have a negative impact on your website's ranking. Regular monitoring of backlinks and removal of low-quality or irrelevant backlinks is important to maintain a good ranking.