Welcome!
I have found it helpful to cook extra portions when I make dinner and then I have leftovers for lunch the next day. I'm careful to separate out my lunch portion before the rest of the meal is served, otherwise my family is bound to eat up the whole thing and leave me with nothing.

I have found hard boiled eggs, cheesesticks, and (later on) full-fat greek yogurt (unsweetened) with blueberries and almonds to be great foods to eat at work. Also you can wrap cold cuts of meat in lettuce with mayo, mustard or cream cheese... and add other veggies if you like. Tuna salad rocks too, if you like tuna. I like to eat mine with strips of green and red bell pepper. That doesn't require any cooking at all.

Good luck!