So first of all besides family reunification your purpose of visit must be valid and non discretionary because they wont give visa to Pakistanies otherwise, secondly invitation letter doesn’t need to be notarized and sponsor can write it in simple english language,you should not attach any...
Its sad, they wont process it, they will send you a letter saying either they refused it or putting it on hold, hope they put it on hold, but for sure you should have selected covid-19 clause if you wanted to get it processed on priority basis