Actually, I wouldn’t really doubt that He spoke in Aramaic.
But the notion that He was installing Peter as the foundation rock is absurd.
I'm sure that Jesus spoke in the language that the locals understood...Whether that was Aramaic or Greek or something else seems to be controversial, still...
Obviously the OT originated in a few different languages but God chose to have it translated and preserved in Hebrew...
I don't know enough about Hebrew or Greek to translate any of it...But I can and do read what the so-called 'experts' write...And in my view, there is far more evidence that Matt. 16:18 was written by the Apostle in the Greek language...