Can you help me to check my grammar ?

Hi !

I need your help! Can you tell me if these sentences are correct ?

Some people consider baldness as a disease.

During the later stages, all symptoms disappear.

When a patient is ill, bacteria invade the heart and the brain.

_Heaven and _hell have no place in his philosophy.

I’ll go with you as far as the hospital.

_Rat can be a dangerous animal

The languages of Europe practically all belong to the Indo-European group

I am speaking as a doctor, not as the chairman of the Medical association.

_Vowel sounds are differentiated by different factors.

There is a Mr. Burnham to see you sir.

I'm not sur that I correctly use article : a/the or _

Thank you so much for your help.

See you.