This is the 134th most frequent Dutch word.
beetje
A little; a bit.
Here, 'beetje' is used as an adverb modifying 'moe' to indicate a small degree of tiredness.
Ik ben een beetje moe.
I am a little tired.
In this sentence, 'beetje' functions as a noun indicating a small amount of help, enhancing the polite request.
Kun je me een beetje helpen?
Can you help me a little?
'Beetje' is used as an adverb in this sentence to express a slight degree to which the painting is crooked.