What are the parameters which effect on speed of Power BI

Which parameters affects most on executing query using PowerBI?
What is important on server side? Do HDD disks slows very much and choosing SSD is much better?
Is any standards that mysql DB should fulfill to to make Power Bi run faster?
Is there options/settings that I can turn on/off on user site to speed up downloading data?
Which functions should I avoid in writing queries?