Do this to improve your English pronunciation:
Say "Red lorry, yellow lorry" 3 times minimum without stopping .
Speed up until it becomes a natural sound for you.
Once you can master this, three times non-stop, as fast as me, you will say these sounds naturally when you speak English.
Tongue twisters are speech exercises which help you master clarity in English. They are like gymnastics for the mouth and also train the brain to retain unusual English sounds. Practice makes perfect!
This is a good exercise for French speakers because this sound doesn’t exist in French but can be helpful for many other languages too!