Please check the following sentences.
1. There are many respectable teachers in my life.
2. They always help me with no repayment, so I appreciate them from the bottom of my heart.
(Not a Teacher)
1) Grammatical, but sounds odd. Here's how I'd write it:
"I've had many respectable teachers in my life."
2) What you've written works, but here's hoe I'd express it:
"They always help me and ask nothing in return, so they have my undying gratitude."