Ramases

Hi,
I've recently bought a dell "mini" 3ix, can't say I'm satesfied with it cause of the following problems,
firstly, I have been searching in the phone for a clue to how change my background to a more colorful one or so but found none. Is there any way doing that at all?

Second, I have some serious problems with the phone's memory. I have a 2GB micro sd in it and it seems to read it, because it says I got 1900 MB and 1500 of it is avaiable, yet, I can't download any thing to this phone and sometimes it closing me apps using "unexpected error" (which comes very often with apps) because in the settings it says that all my phone initial memory is in use, I have been trying to delete almost everything from the phone such as messages and audio files and photos but the memory in use perceantage won't go lower than 90-100%. is there a problem or I just need to configure this somehow in the settings? cuz I didn't found anything related to memory xonfiguration on the phone.

Please answer with simple words. ty.