Hello, i have a project in app inventor and i wanted to know how to retrieve two values from two different users and compare them and if they are equal do something?
Welcome
What is possible depends on what your app does and how it generates and saves 'values'.
Does your Project use a database that different users share in common? For example CloudDB, FirebaseDB, Googlesheets on Google Drive, etc.) Then you can
but if the users do not have the ability to share data with a common database, you cannot.
You need to either have each user saving to a separate 'tag' (if using Firebase) or be able to discriminate using the data base who posts which values.
If they share a common database you can use If..then Blocks and the Math or Compare blocks to determine if the 'values' are equal. See Programming Your App to Make Decisions
It uses firebase to store the information from the 2 users. My app is basically like tinder but the users choose between movies and their selections are stored in the firebase. It is currently only between 2 users. I want to retrieve both their data and compare them how do i do that?
See here:
and post the (relevant) blocks.
We currently do not know. If you share an image of your Blocks, someone might provide a specific recommendation. What you say you want to do is probably possible. 
Okay i will edit the post with the blocks tomorrow
Also how you firebase data is secured.....(or not)