"Grandfather is good at telling stories."

Translation: Farfar är bra på att berätta historier.

[ZoeDantz]

Why both the på and the att here?

[Arnauti]

att is the infinitive marker.
In English, you sometimes use the infinitive where we do, and sometimes the gerund as here.
If you use the infinitive, you too use the infinitive marker, which is to in English: I like to sing or I like singing. So att has the same function that to has in English sentences like 'I like to sing'.

[Wattsin]

Where does "pa" function in " "I like to(att) sing?"

[Arnauti]

There's no på in 'Jag tycker om att sjunga' just as there's no at in 'I like to sing' :)
The prepositions come with the first expression so it's to be good at which includes 'at' and att vara bra på which needs på.

[ZoeDantz]

Tack!

[JohnLittle681919]

I tried "berättelser" for "stories" here: "Morfar är bra på att berätta berättelser". Is there any particular reason it was marked wrong?

[Zed480516]

I have the same question.

[MrBadlands]

I think "berättelser" means more like a story you read in a newpaper and not something you would tell to your grandchildren

[KarelV]

Är det inte bra svenska att säga "Farfar är duktig på att berätta historier." ("duktig" i stället för "bra")?

[lovele4rnin-]

Hi KarelV. This might help you: https://www.duolingo.com/comment/21283756/Bra-vs-Duktig

[Kelly505927]

How do you know if grandfather is farfar or morfar? I translated a sentence and it counted it wrong when I used morfar instead of farfar