Verb conjugation of "beurteilen" in German

I know it is a little confusing. The problem is if the original word is a conjugated verb: I skipped them until now. I did not write it in my explanations. It actually must be skipped. Thanks for noticing.
Productivity declines when it is too hot outside. Oscar therefore closed his laptop and production unit and headed towards the lake where his pretty girlfriend was waiting for him. Once he arrived he bought a ice cream as a surprise.
Now I am learning by other means, such as reading and writing. I can not begin with conjugation training because I lack the basic knowledge. How are you learning at this site and which is your best lesson?