Ha ha ha or correcting your child's pronunciation problem.

Oh, No! My child pronounces some letters wrong. Should I bring him to a speech therapist? He is just 4 years old.

Don't run to a therapist yet! Many of the pronunciation problems could be corrected  by parents themselves, as I learnt by trying to do so.

My son did not pronounced the Russian letter "X" at all. It was produced closer to the Russian "C" at the front of the mouth instead of throat. I tried to find a combination of the consonant (Russian"X" sounds like "H" in "Harley") and vowel that makes the use of the same place in the mouth for sound production and I came out with Russian "XA" (means laughter "Ha ha ha" in English). We were practicing this Russian laughter sound "XA xa xa xa". It was so much fun for him, so after a week he told me:  Mama, listen " XA", "Xarek" (means "weasel" in English)! His pronunciation was perfect! I had to remind him for a month or so about the correct pronunciation, as he could not control it in the speech all the time. The fact is that the problem is gone.

I am sure in your language you can do the same, as I also was able to find a letter combination in words, to practice the correct pronunciation for Italian sounds for my American friend.

Do not push it too much, try once if the child does not want to repeat after you, take a week break, and in the mid time just find something to read that has some of those problematic letters in it.