i just bought samsung galaxy s4 mini last week. today i downloded my fifth app and i sw low internal memory. i checked and the ram was 180MB (plz what should i do?.... only 5 apps!!!!

It's not how many apps you have already downloaded, but the size of the downloaded apps.
Do you have a memory card inserted? If not, get a 32gb memory card(expandable to 64gb) and download link2sd app and send all non system + non widgets apps to sd.

i have a 4gig memory card. i have transfered all my apps and widgets to my memory card. tha apps i have re bbm, whatsapp, picmix, facebook and camera360. all these are low apps. my internal memory is 180mb

I think ure mixing up Rom with RaM

see ure phone has 8gb internal memory and 1.5gb. my phone has 4gb internal memory and 512mb ram. my phone hangs. but it was not so bad until after installing 52 apps. I had to unistall all to bout 7. so I dont see any reason why u should be having such problems.