Usually, in an language, there are some tongue twisters which can help improve your pronounciation. There are those which are for beginners, intermediate, and advanced. Some examples could be seen below.
English Tongue Twisters
'Which wrist watches are Swiss wrist watches?'
'Rory the warrior and Roger the worrier were reared wrongly in a rural brewery.'
'Six sick hicks nick six slick bricks with picks and sticks.'
'Fred fed Ted bread and Ted fed Fred bread.'