iPhone wifi and connection problem

Hi!
Anyone who can solve this weird problem. I have an iPhone 3G which had wifi problems from start. It could not find any network unless very close to the router and also in then it was very unstable. Thus I haven't bothered to use WiFi since I have had good 3G speed where I lived. Now I changed country and ran a jailbreak and unlock. I have voice working on my new SIM card but I have no 3G data connection......could be something with the jailbreak????

The strange thing is with wifi ..I have to be close to the wifi router...as above.. I get no internet connection when using Safari....but I noticed I get internet for typically other pre-installed apps such as mail, appstore, itunes, weather app, etc. But it doesn't work for Safari or other downloaded apps.

Anyone who has a clue for both problems above (I have reset network settings, I have checked that I have the right bundle etc. etc. for 3G Data connection). And why Safari and other downloaded apps cannot get internet?