Almost 4 year old has great clear speech but very minimal and basic understanding. Has trouble with instructions. Can be extremely impulsive with touch/ speech. But can repeat absolutely any word you say or he hears, witch is great but gets him in a little trouble he's heard bad language once or twice and it stuck in his head like glue and due to the impulses he's constantly using foul language. We have tried correcting this behaviour but due to the lack of understanding etc his behaviours are extremely hard to change.
Advice is welcome