20month old and behaviour

[Alibongo33]

Hi,
My ds is 20 months old and I am struggling to get my him to understand the word 'no' .

He can be quite strong willed and destructive. He throws his toys around, messes up his elder sister's games. Throws things over the stair gate down the stairs. He doesn't actually seem to play with any toys as they are designed for.

I seem to be constantly saying no but he just laughs. Never had this situation before. My dd understood the word no even if she continued to do it which wasn't that much.

Any advice please

DD found the word No funny and it had the opposite effect.

What worked (somewhat) better for her was saying "not throwing" instead of "no" and also saying something she could do instead eg "not throwing truck, only throwing a ball" or "not throwing truck, only rolling it on the floor" etc.