doll
great
Colloquial for great, awesome, or fantastic.
Das war eine dolle Überraschung, vielen Dank!
That was a great surprise, thank you very much!

great / intense
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great
Colloquial for great, awesome, or fantastic.
Das war eine dolle Überraschung, vielen Dank!
That was a great surprise, thank you very much!

'Doll' does not mean the English word 'doll' (toy doll). It is a colloquial word for 'toll' (great), 'stark' (strong/intense), or 'verrückt' (crazy). The German translation for the toy figure is 'die Puppe' (the doll).
Das war ein dolles Fest gestern Abend!
That was a great party last night!
The word 'doll' is used almost exclusively in spoken, informal language. In written or formal contexts, it sounds inappropriate.
Meine Oma findet meine neue Frisur ganz doll.
My grandma thinks my new hairstyle is really great.
'Doll' can be used like 'sehr' (very) or 'stark' (strongly) to intensify a verb. In that case, it stays unchanged and is not declined with the verb.
Ich habe mich doll erschrocken, als du gerufen hast.
I got really scared when you shouted.
very
'sehr' and 'doll' can both be used as intensifiers. 'sehr' is neutral and understood everywhere, including in formal situations. 'doll' is colloquial and sounds casual; in this use it means something like 'very' or 'really'. You are more likely to hear it in spoken language than in official texts. In addition, 'doll' can also mean 'great' or 'wild', depending on the sentence. If you want to speak safely and neutrally, use 'sehr'; for casual everyday language, 'doll' can fit.

Wegen des langen Arbeitstags bin ich heute doll müde.
Because of the long workday, I'm really tired today.
Die neuen Schuhe gefallen mir sehr.
I like the new shoes very much.