zeigen This means "to show". The thing which you are showing is in the accusative case. The person to whom you are showing it ("Ihnen") is in the dative case.
was darf ich Ihnen zeigen? What may I show you?
das T-Shirt (-s) T-Shirt
suchen to look for
die Baumwolle cotton
aus Baumwolle made of cotton
selbst This means "self" i.e. the full question reads: "Would you like it for yourself?"
verschenken to give sth as a present
der Geburtstag (-e) birthday
wann hat sie Geburtstag? when is her birthday?
Januar January
am einunddreißigsten Januar on the thirty-first of January
die Farbe (-n) colour
welche Farben...? which colours...?
hellblau light blue
dunkelblau dark blue
die Größe (-n) size
welche Größe muss es denn sein? which size do you need?
klein small
etwas kleiner als ich a little smaller than me
(Größe) S small (size)
ich glaube so Größe S I think she's a small size.
(Größe) M medium (size)
reichen to be sufficient
S reicht "Small" will do
Sehen Sie mal Look!; Here you are! (= polite imperative)
rund round
der Ausschnitt (-e) neck (of shirt)
mit rundem Ausschnitt This means "with a round neck". Note the strong adjective endings on "rund" as there is no article preceding the adjective.
schauen This is another verb meaning "to look" or "to see".
preiswert good value
ein preiswertes T-Shirt a T-Shirt which is good value (for money)