Getting error: The XML for Analysis request timed out before it was completed.

Hi Guys,

i am getting below errors. I have linked Power bi wth an excel sheet which is stored on sharepoint. I have heavy complex DAX, calculated columns, Power query formulas. I have spent 10 days researching what could be the issue. I know it has something to do with huge data but my pbix file is just 4 mb. The power bi experts have suggested me to break the data and optimise but trust me its complex formulas and i dont want to disturb that. Below are the errors i am getting.

Error in Power bi service:

The XML for Analysis request timed out before it was completed. Timeout value: 7200 sec. Table: ___

Resource Governing: This operation was canceled because there wasn't enough memory to finish running it. Either reduce the memory footprint of your dataset by doing things such as limiting the amount of imported data, or if using Power BI Premium, increase the memory of the Premium capacity where this dataset is hosted. More details: consumed memory 16359 MB, memory limit 16324 MB, database size before command execution 59 MB

If i try to refresh from Power BI desktop , the refresh is never ending and i am not able to know which exact column is creating an issue. I am confused whether there is an error in data model or its a space issue. 

Any expert ...Please suggest