I have to tell you, I tried to understand it.
( ( I ( have ( to ( tell you ) ) ) ) ( , ( I ( ( tried ( to ( understand it ) ) ) . ) ) ) )
(ROOT (S (S (NP (PRP I)) (VP (VBP have) (S (VP (TO to) (VP (VB tell) (NP (PRP you))))))) (, ,) (NP (PRP I)) (VP (VBD tried) (S (VP (TO to) (VP (VB understand) (NP (PRP it)))))) (. .)))
I did my best to understand it.
( I ( ( ( did ( my best ) ) ( to ( understand it ) ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBD did) (NP (PRP$ my) (JJS best)) (S (VP (TO to) (VP (VB understand) (NP (PRP it)))))) (. .)))