Are people who are learning english find it harder to understand english with an accent even more than a normal british/american accent?

Depends whether their teacher speaks with a British accent or not. In Japan, most English teachers are American, so Japanese speakers learn the American accent. However in Europe, most of the English teachers use a British accent, so most Europeans speak English with a British accent. Early students will always have problems with accents. I'm learning Chinese (Mandarin) and my teacher is from Taiwan, so she sounds a lot different than someone from Beijing, which is supposed to be the "official" accent. However I prefer my teacher's accent because...well...she's also my wife.

It could depend on the accent. The easiest among native English speakers are probably middle class BBC English, middle class East Coast US and middle class southern Irish. South African English would be much more difficult, as would be Indian English. And don't even think about Glaswegian, or Geordie, or Norn Iron (if you know where that is!) The worst English teaching I've ever heard was by an Italian who spoke English with a very strong accent indeed. I winced, and felt so sorry for his poor students!

Almost certainly. Non native English speakers certainly have difficulty understanding native speakers from parts of the English speaking world where the accent, usage and everyday vocabulary differs from the one they have learnt.

Hence the rise of Globlish: the international English foreigners, particularly business people, use between themselves: no slang, no in-jokes, no words peculiar to only one part of the English speaking world, and above all, no one has the advantage of using their first language. In Brazil in the 1970s I remarked to a Brazilian publisher on the number of technical textbooks on sale there in English, imported from Russia. He explained that even in written English, it was easier for a Brazilian to understand the English of another foreigner than either US or UK English.

i thin, u'll find it harder to understand f ur listening to an english guy speaking english. they speak too slang, with very hard-to-understand-fast accent.