I would like to ask few question.
1. What we can do to decrease CPA?
2. How many sitlinks we can add on campaign level & adgroup level?
3. What we can do to increase the number of conversion with same budget?
4. How many account we can add in single MCC?
Welcome to AdWords community
Here is answers of your questions:-
#1 & 3.
In order to reduce the CPA and increase conversion, you can run the search query report and add the best performing search term and also exclude the irrelevant searchs. Also pause the low performing ad copy and keywords that are not giving ad copy. Write the relevant ad copy in campaigns with respect to keywords.
Ad group levels you can add upto 20 sitelinks.
Please follow the below link for account level sitelink:-
You can find the similar thread in the below link:-
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