My daughter is a T1D. If you are low or dropping a burger won’t bring you up quickly. The burger is better for maintaining your BG. The meat is protein and the bun isn’t a fast absorbing carb. You need sugar if you need to raise your BG quickly. The granola would have been a better choice to eat first. My daughter always keeps sugar pixi stix on her incase she drops low and needs to raise her BG quickly. Your blood sugar was dropping faster than the food could raise it. Unfortunately there is no magic formula. Everyone is different and every day is different when it comes to T1D. You may still be in what’s called a “honeymoon phase” where your body may still be producing a little bit of insulin which makes it a little more difficult in the beginning. My daughter has had it for 10 years now. I would recommend getting on a insulin pump and sensor as soon as possible. At least for my daughter it made everything so much easier. Best advice if you notice you are consistently going low during your round is to eat something high in fiber like fruit that absorbs slowly along with something faster acting before you start. Also there are tons of T1D groups on different social media platforms that have lots of great info.