Welcome to #mathteacherlyfe.
Make it easier on yourself by keeping it simple and getting your classes into a routine. When mine arrive, we always begin with a problem solving activity (2qs (hard/normal) on the board before they enter, they know to come in, plonk down and get started straightaway). It gives you 5 mins to get the roll marked.
Next 15-20 is direct teach, introduce a concept, copy down any key terms etc,
Show the concept once, show again (have them write this down as the exemplar), then do one on the board together.
Then, independent work for the next however long, wander round, help those that struggle. Then answers/homework etc in the last 10mins. All the new-fangled teaching methods aside,
I find having a predictable routine works best overall.
Ps- no matter How good you are, sometimes kids are jerks. Don't take it personally. You'll get very good at smiling and speaking in a calm voice while wanting to throttle someone.