How do you feel when someone presents a speech with so many grammatical errors?

Handle the situation with "sensitivity", a teacher can "correct" a student, that after all is the role of a teacher and no offence wiil be given or taken. Always important to explain WHY they have got it wrong and give them the opportunity to correct their speech themselves, if at this point they are still unable to get it right, tell them the correct way. If in conversation with friends or colleagues and the same situation arises, OFFER advice but do it in such a way that they can see that it is for their benefit and it is not just you demonstrating how clever you are!! 

According to situation; we were never born well educated.

If I understand him , no problem.The most important of a language is communication.If I don't understand , I will be confused and I will ask questions to understand.

OK. If it is my student - correct them. If not, smile and nod

I had narrowed down my question  to what is in my Specialities.................l am not sure what kind of editing the Bayt.com specialities did to my question.Anyway,whatever you did,thank you innumerably.

For a student I'll correct his mistakes ,for my colleague or managers or others will try to understand and if I did not understand I will ask him to repeat his words and may correct its mistakes then.