Suggest following the advise fro @ Kurt Lang -->> First.
Only after doing the above actions and if still having a Slow Computer there are a number of Other Factor that could come into play including Third Party Applications and Lack of Empty Space on the Drive
To get a possible better look -->>
Download the Application Etrecheck directly from the Developer.
The application is free or paid from added features.
It will take a Snap Shot - both the hardware and software.
The Report will Not Reveal Any Personal Information.
Post back the Full Report - copy and paste ——> using the Additional Text Icon ( 3rd Icon to last ) <——
We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.