Learn Romanian: Doctorul mă ajută.

In Romanian, the word for "the" attaches to the end of the noun instead of being a separate word. Doctor simply means doctor, and adding the suffix -ul makes it doctorul, which means the doctor.

Why is mă placed before the verb?

In English, we put the pronoun after the action, as in "helps me". In Romanian, short pronouns like mă (me) almost always go directly before the verb. Literally, the sentence structure is "The doctor me helps".

If ajută is used here for the doctor, how would I say "I help"?

The form ajută is the "he/she/it" form of the verb. If you want to say "I help", you use the form ajut. For example, "I help the doctor" would be Eu ajut doctorul.

Could I use mine instead of mă to say "me"?

Not here. Mă is the short form of "me" that you must use directly with verbs to show who is receiving the action. Mine is the long form, which is only used after prepositions like "with" or "for" (for example, cu mine means "with me").