Yes, 5G towers are all over. You receive microwaves even if you have no 5G phone.

I have read that the 5G phone can boost/concentrate the 5G microwaves, but have not seen a detailed description on how that works.

That is correct. For the most part, cell phones are just fancy radios that recieve and emit radio frequencies (electromagnetic waves/energy). The energy sent out is put out in all directions and comes in contact with people whether they are using a cellphone or not. When you are talking on a cell phone, you are putting a radio right up against your head and enitting radio waves ( electromagnetic waves). The higher the frequency the smaller the electromagnetic waves. some of these waves are supposedly so small they can enter your skin and affect you. also something to look up is resonance. what happens when a frequency resonates at the frequency of items, cells, glass, etc.