Hi Zoghumoil46
You can go to the Rhein-Center using the Tram Number 8 from Basel SBB to Weil am Rhein, Dreiländerbrücke.
This ticket is called “TNW triregio Einzelbillet” cost around CHF 3.10, you can Buy it in The SBB Mobile App or at the SBB Tickets Machines in the Basel SBB Station probably also at the TNW
Tickets Machines. Just select the “GA” Discount there, so you don’t have to Pay the Swiss Part. If you are leaving the “Rhein-Center” and walk 200m to The Boarder to the Stop “Basel, Weil am Rhein Grenze”. You don’t have to buy a Ticket because the Stop is in the GA Area, Please Note this Trick does only work at the route from Weil am Rhein to Basel! From the Stop “Weil am Rhein, Dreiländerbrücke” you have to pay, because the Stop is not in the GA Area, I guess there is also a Ticket Machine at this stop.
Kind Regards
Apfelmus_CH