Any one can help me distinguish Diese from Dieser ? Both of them mean " This" but am i correct to think that Diese+ Feminine Noun/ Plural noun while Dieser+ masculine /neuter Similar for Dieses and Dies: Dieses+ masculine/neuter Dies+ feminine/plural Danke sehr
They have the same ending that the definite article would have in the same place.
For example, der Mann, die Frau, das Kind, plural: die Kinder
dieser Mann, diese Frau, dieses Kind, diese Kinder
That was only the nominative case, but this trick works in other cases too. den Mann -> diesen Mann (accusative case)