"Het meisje draagt een trui."
Translation:The girl is wearing a sweater.
The ui-sound is very common, but can be considered a bit tricky for foreigners. It lies somewhat between the [oi]-sound of "boy" and the [ai] of "guy". That's only an approximation though, and you will be recognised as not being Dutch with this pronunciation, but I wouldn't think too much about it. People will understand that you're learning.
The r is pronounced as you normally would in the middle of a word: a guttural r in the back of your throat.
If you want to improve your pronunciation, I'd recommend you to start listening Dutch audio materials; especially youtube can be a good source.
the t is pronounced like in english but without the puff of air, so like in 'stop', not like in 'top'.
with the r, you may choose any of the r's used in the dutch language, the most common ones are, the one used in english, the gutteral r that Hermesianax was talking about or the rolling r as in spanish. Unlike English however, the t before an r doesn't almost become a 'ch' as in 'chair'.
as for ui, one of the more difficult sounds in the dutch language, I would recommend saying it as a diphthong starting with the 'a' as in 'cat' and ending with a rounded lips version of the 'ea' as in 'sea'