What is the smallest Size i need for a Mobile page?
Iphones are so small but they should also be able to read my page.
Right now i have the smallest 380 (to 320)
You should be good with the minimum width of 320.
One recommendation: try to use breakpoints as little as possible. Saying this because the distance between 380 and 320 is very little.
It is possible to use only one fluid width breakpoint at 768 with its minimum width of 320.
This depeneds of course on your design and your needs.