Is it my impression or it is missing letters in the course? I've finished all the alphabet on the app and didn't learn the equivalents of F, P, N, S, X, Kh and so on...
Well, I'm not sure about how the course goes myself, but surely Arabic has no P or X, nor V or G - Unless you use X here for the German (Ch), but you've already typed "kh" which is خ and some people prefer to write this as "x"
N = ن
P and b are the same in Arabic (most often it is voiced though so yes it is a more similar to a "b") both = ب f = ف
Kh = خ
Arabic doesn't have "V" but it is sometimes represented as an f, or as " ڤ " (with 3 dots on top) as a lone letter from other languages. This is not an Arabic letter though.
Alike the B/P situation Arabic also doesn't differentiate between J and G and uses ج for both. In Modern Standard Arabic they pronounce it like the french "J" or the "Sh" sound in pleasure. In some dialects like the Egyptian they pronounce the letter like a hard g, as in the word great.
I've just finished the four 'alphabet' sections, and noticed that it hadn't covered some of the letters, namely ص ض ف ق ث ع غ ه خ ح س ش ن ط ظ ذ ء
But when I got to the next section 'descriptions', it expected me to know what ع is, and also how it's represented in Latin transliteration, ie; 3. I was already familiar with this from learning some Arabic before, but it's not good for a course supposedly teaching Arabic from the beginning.