In case the teacher can't hear you, your microphone on the browser may be disabled. You have to give permission for the Microphone to be able to use the classroom application. 

Go back to the Dashboard/Homepage by clicking on the Tanzeel Logo (top Left), wait for 10 seconds, click on "Go to class" button again.

Here are some articles you may want to read depending on what applies to you:

MacBook/iPhone/iPad Users using Safari Browser:

Control access to your microphone on Mac 

Change Websites preferences in Safari on Mac 

iPhone users using Safari Browser

Computer/Android users using Chrome Browser:

Using Chrome on Computer

Using Chrome on Android

Computer/Android users using Firefox Browser:

Using Firefox on Computer

Using Firefox on Mobile (Android/iOS)