Error when importing a large table in Power BI Desktop

Hello! 

I know that this topic has been mentioned previously but I still have a couple of questions regarding it: 

In the last couple of days I have tried refreshing the biggest table in my dataset but all tries took me about an hour and I received the error:
"Failed to save modifications to the server. Error returned: 'There's not enough memory to complete this operation. Please try again later when there may be more memory available.'"

I tried removing relationships, calculated columns and imported columns from the table and I still hardly managed to refresh it.
The whole dataset is only about 3GB. When I do a refresh however it can be easily interupted or i get the no memory error.

My questions are:
1. What operation from the listed above has the greatest calculation costs
(having many relationships, many rows/columns, calculated columns)?
2. Would a computer with more processing power solve this issue? 

Thank you in advance!