the waltz you said is played in this scene https://www.youtube.com/watch?v=RTFPMpY0W5w. you can search it like: “ in einem kleinen café in hernals Piano” , greetings from Mexico and thanks for the name of this waltz
you can hear the same melody between 2:00 and 3:00 in https://www.youtube.com/watch?v=uLq3ixjsWJI