Trilling and other Terms

I printed off "Eine Kleine Nachtmusik" by Mozart a few days ago, but it has the letters "tr" above some slurred notes. Sometimes, there might only be two notes, like a G and F# on the E String slurred together (Beat 1 of Measure 6), but there`s also a G to F# to G to A to F# in one slur (Last 1 and 1/2 beats in Measure 18).
The first G is a sixteenth note, the F# to the second G are both 32nd notets, and the A and last F# are eighth notes.

I play these really fast, but it still doesn`t sound like the CD that I have. Do you play the G to F# really fast several times, like grace notes in 1 beat?

Also, this is my fifth year in a strings course in school (5th grade to 9th grade).

Trilling and other Terms

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