We have Base Lang = EN and additional Language Swedish

When I log in via my ipad i got some text in English and some in Swedish.

What is Mobile looking at to se the language in the mobile app?

The WO card looks OK

If I open the WO there are some additional fields, Ownergroup, FNLConstraimt and custom field Preparation Box.

And the description is just displaying the Base language description.

The ESTDUR field is picking up the Swedish description.

IS there anything I need to do to get the Swedish descriptions on added fields in the mobile app?

If you provide a label on the smart-input, you need to also build the translations into the other languages. If you already have titles in MAXATTRIBUTE that are properly translated, make sure the label is not defined on the smart-input and it should then pull from Maximo. 

If you're developing on 8.11, there's a developer documentation link in the help menu that covers Localization with the labels.json. The labels.json in English will exist in the src folder in a i18n folder. If you go up from the src directory to the public directory, you'll see the translation files for the various languages we support. If you need to use labels this is how you'll translate it.