Simpler overview: There are two groups of inflections. 1) A noun phrase changes by gender, number and case. A noun phrase consists of a noun, optionally with an article (der/die/... or ein/eine/...) and an adjective. This also includes pronouns (as substitute for nouns) and words that replace the article (kein/keine/..., viel/viele/... etc.). These changes are NEVER by position. The gender is an attribute of each noun (learn it together with the noun, i.e. "der Tisch", not "Tisch). Number is the same as in English, and the case is determined (1) by the verb pattern ("jemandem (Dat) etwas (Akk) geben") or (2) by the preposition in front. Some prepositions require always the same case, some can take several ("Wechselpräposition"). There are four cases in German, not two (Nominativ, Genitiv, Dativ, Akkusativ). 2) A verb changes by number, person, tense and mood (Indikativ/Konjunktiv). You really need some grammar resource for German. http://www.mein-deutschbuch.de is a good introduction (but in German). Canoo (http://www.canoo.net/index_en.html) is also available in English, and great for reference, but too detailed for learning.

Actually, there are many questions you are asking so let us have a look at prepositions and verbs first: Some perpositions , are only used with ONE case. Example: zu and mit require Dative case: Ich spreche mit DEM Mann. Ich gehe zum ( = ZU + DEM ) Bäcker. Others, like the preposition in can be used with DATVE OR ACCUSATIVE case: NOTE: The question "Where" > Wo? is always followed by DATIVE, since we are talking about a place: WO bin ich? Ich bin IM Zimmer. > I am in the room. WO ist Anna? Sie ist IM Garten. > She is in the garden. Im is a combination of preposition + article: in + dem > im likewise: zum = zu + dem (See above). The question: Where to? > Wohin? requires Accusative case, we are talking about a movement: Wohin gehe ich? Where am I going? Ich gehe in das Zimmer. Wohin geht Anna? Where is Anna going? Sie geht IN DEN Garten. This might help: http://www.graf-gutfreund.at/daf/02grammatik/04praeposition/gr2_praepositionen_ueberblick.pdf http://www.graf-gutfreund.at/daf/02grammatik/04praeposition/gr1_praepositionen.pdf Another important part of speech are verbs. They have different endings for each person and you should learn these endings by heart. Have a look at these two verbs: kommen , gehen . These forms are called infinitive, that is the basic form of a verb. most infinitives and in -en. When we leave out the ending, we get the stemm of the verb, to which the personal endings are added. Here are the present tense endings: komm- ; geh- = stemm ich komm + e > ich komme du komm + st > du kommst er / sie /es komm + t > er / sie /es kommt wir komm + en > wir kommen ihr komm + t > ihr kommt Likewise: ich gehe, du gehst ....... Link: http://www.graf-gutfreund.at/daf/02grammatik/01verb/01indikativ_aktiv/01praesens/gr1_konjugation.pdf