It's common for forge to take long to load depending on number of mods and PC quality.
3+ mins for a average PC to load 20 mods in my past experience.
15 mins to load the largest modpack I've ever come across (400+) on my new good PC.
So yeah, common for it to take a while. Try closing other things to save CPU and RAM.
Edit: Yeah as for it saying 'not responding', even vanilla does that too. Not entirely sure why, probably loading the many GB of game assets/libraries. Completely normal.