Can and do beings from the higher realms communicate with us?

sumbodhi wrote: “Saññā seems to be helpful. Does the Canon mention about such communication and why it happens. What reason would they have to do so? To help someone??

You seem to be referring to communications that happen without “talking”, but with saññā.
– There are many living beings who do not have physical bodies ours. So, there are no mouths, tongues, etc for talking.
– Those beings include some lower beings in peta realms as well as Brahmas in Brahma realms. For example, when Sahampti Brahma communicated with the Buddha right after his Enlightenment, that is how they communicated.
– Such communications are not common, especially with Brahmas. But some lower beings seem to communicate with people with “bad gati” and get them to do immoral things. Also, there could be devas in lower realms trying to help people with good gati. I personally have had no such experiences.
– Did you read about it in a post? I do not remember the name of such a post. If you know what it is, please post the name (with a link if you know how to). That will help others.
– One post with some relevance is, “What Does Buddha Dhamma Say about Creator, Satan, Angels, and Demons?”

sumbhodi asked: “why would gandhabbā communicate with humans?”

I am not aware of specific cases of human gandhabbas communicating with humans.