Writing and Communication

you are likely to start with pictographs of some sort, a very primitive form of written language that eventually gets more and more refined over time resulting in a written language. To begin with often you should make pictographs of commonly used and seen objects, creatures, terrain etc and draw them, overtime just as the hieroglyphics of the Egyptians turns into more refined letters do to a need of expediency in every day life a curved stroke of a character here or a shorter brush there eventually resulting in letters/characters rather than full on pictographs/hieroglyphics

for spoken language often onomatopoeia or the mimicry of natural sounds made in nature to denote what you were trying to get across was a start from my understanding along with hand movements and charades eventually we would move from that to coagulating such noises into more defined phrases or terms

i would look up conlangs and the subject of their origins and how to make one yourself as its effectively the same thing in alot of ways

along with phonetics

since i am not an expert on the subject though i will leave this to someone more inclined and knowledgeable

my online name is Forteko you can contact me on my discord if need be but this was my contribution and guidance to head start this page