> If I have troubles receiving SMSs from Germany to German number while in US, would wifi calling icrease the chances of receiving the said SMSs?

I'm not up to date on the state of messaging infrastructure but it used to be the case that some providers would offer non-standard methods for sending messages over their network to intermediary providers. Rather than sending an SMS to a number, a business would ask the intermediary to send a message and the intermediary would use the non-standard method provided by the network provider. The non-standard methods work fine if you're connected to the network directly but if you're overseas that will not be the case and so you can't receive these non-standard messages. Don't quote me on any of that, though.