Different Gender in Nouns
Is there a reason that nouns in German have different genders? (Example: "die Suppe" or "der Apfel")
There's no reason if you mean someone planned it that way. Lots of languages have noun gender. You just have to accept that's the way it is and be sure to learn the gender along with the noun. Learning the plural form at the same time is pretty useful too.
Don't get hung up on the word gender. Just think of them as different categories of nouns.
Apart from German, languages like French, Spanish, Italian all have noun genders, originating from Latin. They're basically loose categories in which to put nouns, for example, abstract concepts are feminine in most of these languages. In some cases it is necessary to specify the gender in order to differentiate between possible meanings, for example in French
la tour (fem.) means the tower
le tour (masc.) can mean the turn
So you'll have to start out by learning the genders along with the words, and eventually you'll get a vague understanding of how these categories work. Vague because even native speakers won't be able to tell you why apples are male and potatoes are female
Unfortunately, you have to memorize them because they are VERY imortant because of 4 different cases where the article change its form to a new one. Fortunately there are some "roots" where it can be easy to recognize the gender of noun. For example, i know that words that ends in -heit, -keit, -tät, -ung, -schaft (and probably other more) are feminine like : die Qualität, die Freizeit, die Landwirtschaft etc. Another ones that i remember are -um -nis used for neutral nouns (das Ereignis etc).
Some nouns have a definitive gender like male professions (for example der Polizist) the same for feminine (die Kellnerin), all months are always masculine, flowers are always feminine, all materials are always neutral and so on. I have only this in mind but if you go to search on the web, you'll find more detailed informations about "the rules" of these nouns.