Angel, Here is a website you will find helpful. It has an illustrated presentation of prepositions and will help you understand "in, on, at" as well as other prepositions: http://www.elihinkel.org/tips/prepositions.htm.

the usage of the prepositions depends on the previous words

Thank you very much.

I agree with Michael... just by typing "at on in" into Google, this came up: https://www.englishclub.com/grammar/prepositions-at-in-on-time.htm https://www.englishclub.com/grammar/prepositions-place-at-in-on.htm