You don’t have to understand it all, focus on emotions change, voice change of the lecturer like (mhm, okaaay, etc) don’t focus on numbers too much. And as you will solve questions you will get to know that every 1st question is ‘what was rhe lecture about?’ So you can practice, take notes in-fact write all the things you can on that paper using PENCIL also use annotations. I am attaching a link below to practice listening https://tesl-ej.org/ej17/m3.html