I suggest that we may cooperate together for practicing English. We can discuss some interesting issues so we enrich our English vocabulary or we can just have small talk
Let's begin with 68-questions-test in order to determine your level of English language. I've done this exam before and my level is Upper Intermediate
Level Test
You can add some valuable short lessons like clarifying a rule of English grammar, some mistakes that usually people fall in or .......etc
Note: feel free to correct your colleagues' mistakes