People have rules for how you should train to reach your goals. You "can't " do this without that,etc. Truth of the matter is everyone is different. So the results are different. You "can" build muscle while in a deficit. For some you may have to intake more protein. You might need more cardio. You may need to change your nutrition. Maybe your training... But for sure,you "CAN" build more muscle while training in a deficit...

Nobody started perfectly. Nobody knew everything that they know when they started. It's a journey. There is no right or wrong. Only what works for you. Experts and certified trainers just have more experience. But they're not you. They don't know your body and how it functions. Some people can help,but ultimately your in the driver's seat. Take small steps. Celebrate your goals that are achieved.

It's your health. It's your body. You say you want to be better. You say you want to improve your health. You say you want to feel better. You say you want to look better. Do you see the narrative yet? Every year at the start,unbelievable amounts of people all over the world decide that now is the time to work on their health and fitness. Time goes by and... Excuses set in,determination is wavered, and ultimately,people stop. It all starts with the narrative.