Date manipulation

Hi there,

I'm new to ninox and i trying to automatically calcute a date after manually entering a number of month and displaying that information in an additional field. 

So my fields are: 

'Kaufdatum' ("date field") with the date of purchase 

'Garantiezeit in Monaten' ("numeric field") entered manually

'Garantie bis' ("date field") - which should display 'Kaufdatum' + 'Garantiezeit in Monaten' after entering 'Garantiezeit in Monaten'

I imagine it should look something like

'Garantie bis'= ('Kaufdatum') +('"Garantiezeit in Monaten"')

but I can't get it to work. I would appreciate any help with the correct syntax.

Another thing I was wondering: is it possible to have an automated reminder (email, pop-uo or something similar) when there's less than 1 month to the 'Garantie bis' date ?

Thank you for your time.