Let me explain:the concept of going to 2 digits is weird to me: how it was decided that after 9 which is 1 digit, to 10 then 11 which are 2?
There is kind of the same thing in ancient Hebrew where the letter י marks 10,and the letter א marks 1,so 11 is יא If the answer is so obvious please be patient and explain, I'm just curious :)
The FAQ has answers related to numerical systems: https://www.reddit.com/r/AskHistorians/wiki/science#wiki_societies_using_different_number_systems
Especially this one is why many civilizations developed base 10 numerical systems: https://www.reddit.com/r/AskHistorians/comments/2d4g29/why_did_most_civilizations_develop_a_base_ten/cjm6qpm/ by u/Jooseman
Note that your question is simply "why are we using base 10 (decimal) as our numerial system". Having two digits just means that we have a number that can be written in the form 1*x + 0*1, where x is the base of the system (10 in this case). If we were using, say, a hexadecimal (base 16) system, then we would only "go to two digits" after 15.