My son can not say some letters how do I teach him to pronounce them the right way??
Like when he says cup he says it as tup, or car is tar, he has a hard time saying C words and S words can someone please help me...

First how old is the child. If he is in school, see about professional speech help

How old is he?

Most little kids can't pronounce words perfectly until after a lot of practice and after hearing them pronounced correctly. My little brother called Kleenex "Teelee." He also said "waterlemon" instead of "watermelon." Just remember, if you were learning a brand new language, how you would mess up pronunciation at first.

Don't get on his case, but just make a point to say each word correctly and with enunciation (emphasis). Make up silly S or C sentences or poems and say them to him with ssssssssses: "Silly Sally sat silently" or kkkkkkkkkkkes (k sounds) "The kitten kicked over the cup." Then let him try to repeat.

My son will be 4 in August. I have done everything to help him with the words he can say, it dose it for a few min. and then he gets mad and walks away. He speaks in full sentence but you can only understand about 3 words out of the whole sentence.

Your child needs speech therapy. Talk to your pediatrician and get a referral for an evaluation with a therapist.

Do you know if I would be able to call the school and have him evaluated for the speech therapy program at the school? Because I’ve asked his doctor about it and all she tells me is that its normal for his age but I know something is wrong when he can't say some words, like cup is tup, car is tar, and he has a problem with S like his sisters name is shonna but he can't say it so he calls her onna, and I start to work with him and that last all of 3 min and he’s getting mad at me and walks away so I don’t push it on him.

Contact your local elementary school, special education office and superintendent's office. (The squeaky wheel gets the grease.) Don't try to teach your son. Once speech therapy begins, ask to watch a few sessions so you'll know what to do. Practice the activities at home - but make it fun. Both my children had different speech issuse and we'd make a game out of the activities. For one child's issues, we would blow bubbles then pop them while saying the word 'pop'. If your child mispronouces a word, try not to correct him if it makes him angry. Repeat the sentence (or part of it) correctly. For example, if your son said "I want a ookie", you could say "Okay, let's get a cookie." Pronounce the letter 'c' clearly.
Most importantly, don't try to do it alone. Get speech therapy ASAP. Good Luck!

I agree with the previous advice that has been given. I would contact your local elementary school and see what classes they can offer for speech therapy.

I just wanted to tell you that when I was a kid I used to have a speech problem as well and I remember being in elementary school and having to go to classes to fix my speech. Don't worry about it too much. He will learn how to pronounce words right as soon as he starts seeing a speech therapist. Good luck.

In my town of Mississippi our school had a speech class for children how needed it badly