Browsing the map is slow with my rendered own files on local server

Hello,

i rendered my own files (for 2 days) of Germany, but when i use a local server (MapServer) and i zoom to a country level i need about 30-40 sec to update the map in my browser. Is this a common problem and can you please tell me a solution about my problem.

I see there are different applications for Phones that work offline and load the different elements really fast. I understand that having a map on a PC browser and on a small display of a Phone is smth different, but still the PC has more resources as well.

Ty in advanced !