Help/ advice building an ARM based custom board

I am building a board for my soon-to-be startup and need some help from the community on how to approach this. My background is a software developer I work mostly with web based tech stacks but work with a lot of A.I tech stacks as well; I have a solid base in C/C++ but what I do not have a solid base in is hardware engineering, this is something I really want to learn as it's a new challenge and I find it very fascinating. I have tried to get a better grasp using Udemy courses on embedded...

Help/ advice building an ARM based custom board