Eine Möglichkeit : guess

guess

imagine/suppose/assume

e.g.

I only have an inkling about...

I can only think up ideas of what...

I can only imagine that you think you know idiomatic English, hereami. We'll, I am here to abuse you of that notion, based on some of your suggestions - like the one above.

At times I come to the conclusion that you are abusing many a time :)

you are abusing many a time
Verstehe ich nicht. Was willst du damit sagen?

Honey, I know what abuse means. English is my native language. What's yours? Please put it in your profile.
 
What I don't understand is this part of your sentence ... abusing many a time.
Abusing needs an object. dude is in your opinion abusing what?

I think dude knows 'what' :)

Und deine Muttersprache? Kennt er sie auch?

I apologize. I meant, of course, disabuse you of the notion ... This stupid autocorrect is driving me nuts.

... I can only surmise what his words mean.

"Guess" could be right if the speaker has very little information or context. "Surmise" is better if the speaker has more information and context.

I can only imagine what his words mean.