Hi, Johan.
It is not possible to set a different currency per form in Gravity Forms by default, as the currency is a global setting.
There is a third-party paid addon called Multi Currency Selector by Gravity Plus.
You can see it here as advertised on the Gravity Extend website: https://gravityextend.com/gravityforms_plugin/multi-currency-selector/.
I have not used this plugin myself, so I cannot endorse it in any way. I highly recommend you check online for any further information about the plugin and ensure it is the right fit for you or not.
Alternatively, you can leverage the gform_currency filter to intercept the global currency setting with a custom solution. Please note that this filter affects all forms by default; you may need advanced development experience to adapt the solution to your needs.
You can find the gform_currency filter documentation here: https://docs.gravityforms.com/gform_currency/.