This is just some advice.
I have seen numerous times in posts where people are trying to make changes to the base css file via cpanel, or being directed to the base css file. Any changes you make there will be lost when you update your theme since the update will overwrite everything with the original files along with whatever the update contains.
It is always best practice to do your modifications by using the custom css in the admin panel. These changes will not be changed by the theme update since it actually creates a separate css file for the theme.
Of course having knowledge of css, and how to use inspect element are key to finding the elements that you need to change, and what css to apply to achieve your desired result.
There are plenty of videos on youtube on how to use inspect element, and also, plenty of information on how to use css.
You can use inspect element to play around with different css rules without physically changing the css. Once you refresh the page the original css will be re-applied.
Once you find the element that needs to be customized, and you find the correct rule to achieve the desired result, just copy, and paste it into the custom css box in the admin panel.
You won't need to paste everything; just the element,and the rule you changed, or added.
Everyone want's to do different things to their theme. Not all of theme are easy, or possible, but learning how css works, and how to use inspect element are big steps toward finding out what you can do.
I hope this helps, and if anyone else want's to add more advice, jump in.