Mac Intermittent Excel and browser loading issues

[TekSupport]

Specs: Macbook Air 2017

CPU:I5-5350U

Ram: 8GB

Storage: 128GB

 

Looking for what i can run to diagnose the issue.

I have completed a fresh install of Mac OS and updated to 11.4 Big Sur.

I have run Apple Diagnostics to check the hardware.

I have run Memtest86 and have come up with 0 errors.

However i have noticed that in cpu temps in the summary of memtest86 it shows min/max/ave being : 56C/102C/81C.

I am not too familiar with Mac's but this is as far as i have got with tests i have run.

 

The issue that occurs the most is the excel not responding, when doing small tasks as entering into a field and adding columns in spreadsheets that 

Another issue that occurs is that website loading times are very slow at times.

 

both these issues are intermittent.