The default strings on one Gammel Gura is Newtone Heritage 0.12. Or regular 0.11 strings that pull only a few kilos more than NH 0.12.
On lightly built guitars or if you want even softer strings, you can use NH 0.11 sets instead (or even 0.10). All sound good, but the volume decreases with thinner strings. I have stuck to 0.12 which I think sounds good and feels solid and not too thin. Newtone has an online store where you can buy the strings. An advantage is that you know that they are newly manufactured and have not been in stock with me. Although I have seen sets to sell, I recommend that you buy directly from the manufacturer.
The strings have a lower tension than the normal string set. It can be said that the tension of a 0.12 set corresponds to a normal 0.11 set. The strings have a round core, which means that you should never cut the strings before stringing and tuning. Otherwise it may happen that the winding rolls up and you have a string that does not tune in properly. As the spun strings are softer and vibrate more vigorously, you need to have a slightly higher string height than normal on the thick E string and the 12th band, my standard is 2.5 mm. The thin e-string gets 1.5 mm string height at 12th.