u/2BT-600

I don't know if the title is well written (i'm sorry for that). Recently i did an art work (i can't say the "title Word" for some reason) for a friend, and faced a problem, how can i "eliminate" the blur in the images, when i downloaded it, it actually looked fine, them pixels looking good, but when i shared with him on Instagram the resolution became lower, now, i know this could happen, but is there any alternative to share an image/archive to someone without losing a lot of resolution?

Main reason being that he wants to repost it on his account and tag me. Also, i'm sorry if my english isn't the greatest.