When i speak few of my words are very clearly audible.somebody said my tongue falls inside. how can i improve

perhaps you have a lazy mouth. some people use few muscles in there mouth when they speak. Their mouth hardly opens and their words are jumbled. You need to open your mouth. Try working on toungue twisters. Slow down. If it takes you speaking like you've got a mental delay, then that's just a present sacrifice. Hit all of your consanents. Perhaps seeing a speech therapist would be beneficial.