Alaikumassalam wa rahmatullah,
Raima is an Arabic name for girls that means a woman who has strong love and affection for her baby. It is not used in the Quran directly or indirectly, but Muslims can use it since its meaning is good. It can be pronounced in two ways:
(R)un + sm(A)rt + (I)slam + (M)uslim + h(U)mble. Here you say RAA'IMA, there is a pause between the two parts
(R)un + sm(A)rt + pra(YI)ng + (M)uslim + h(U)mble. This is the easier pronunciation with no pause
As for Raina, most of the meanings mentioned on Islamic sites are incorrect and come from non-Arabic languages. The only Arabic word that sounds like this is Raainah which means "overtaker", "overpowerer". It is written as رَائِنَة in Arabic. It can be pronounced two ways like the name above, just substitute "M" for "N". I have not seen it used as a name, but if you like it you can use it. Raainah is an indirect Quranic word.
Raina could also refer to Raa`inaa, which in Arabic means "guide us", but is an offensive word in Hebrew that the Jews of al-Madinah would say to the Prophet, peace and blessings upon him, to pretend that they were believers while secretly making fun of him.