Hello Bebaihoall44
I suggest to buy Swiss Half Fare Cards and Half Fare Tickets.
https://www.sbb.ch/en/tickets-offers/tickets/guests-abroad/swiss-half-fare-card.html
Half Fare Supersaver Tickets may be available, but it is not recommended if you arrive with a flight in Basel. You can take only the selected trains. Discounted tickets are not refundable.
Half Fare Saver Day Passes may also be available, but they are not valid for mountain excursions. Otherwise buy Half Fare Point-to-Point Tickets.
Please note that reservations are mandatory for the Jungfraujoch in Summer.
https://www.jungfrau.ch/en-gb/
Kind regards
Danhiel