It says completed.... Is it really completed I feel like there’s more

I don't think it's finished yet. I looked it up and on myanimelist it says that while it is completed, there are 3 volumes and 10 chapters total so hopefully they keep updating.

If you read the translator note you can see that it is note complete yet

http://www.mangago.zone/read-manga/mystery_for_my_dear_a/mdx/d_v-2-chapter-5/39/

Yeah thanks I went back and read it earlier