Answers: Eat well and healthily, run on sentences, etc.
Just few things I found.
Step-by-step explanation:
Don't say, "That's why it's so important to eat well and healthily." Simply say, "... eat healthy."
The rest of the sentence it is a run-onn.
Consider changing "That's why it's so important to eat well and healthily, ** if you're low on energy or missing essential nutrients, you're much more likely to get sick."
**Add a ; or a period.
"Protein is also ** critical ^ of maintaining a good immune..."
Add *a* and ^part^.