Is it okay to use the present perfect for part of a paragraph? I want to talk about things I have done in the past and also still continue to do and will do all in the same sentence. Thank you
You can use any tense you want. Select whatever tenses you need to make your narrative understandable.
The objective is to communicate, not to be a grammer nazi.
It has nothing to do with being a grammar Nazi. If you don’t select the correct tense, you can confuse your reader and not communicate your point.
As for switching: college essays will likely be looser in this respect than, say, fiction. In any type of writing, though, if you want to use a different tense for a couple of sentences because those sentences need it, that’s fine. It’s using the wrong tense for your purposes (simple past when you want past perfect, for example) or accidentally meandering into another tense completely (you’re telling a story mainly in past tense and midway you start telling it in present) that’s the problem.
Thank you, I will switch tenses as needed while maintaining clarity.
Avoid switching within a sentence. That should only be done by experts. Within a paragraph is not a problem. as long as your meaning is clear (as noted above).