My RAM is 4 GB as well...
Maybe I just need new phone
Thanks for your advise btw
Hmm... Then I can suggest that apk has been damaged during download or, also, it can happen if you are trying to install it on top of already installed older version. But I cant say for sure. If there is no problem with free space or RAM and even not damaged apk, then I do not have any ideas, because usualy everything must be ok in such situation.