Merging two files not working-what am i doing wrong?

The Lawrence of Arabia 4K release splits the film onto 2 discs. The first disc ends at 2:19 , where the film Intermission starts . I cannot figure out how to correctly merge into one file. The output file is the proper size, but this file thinks it’s only the first half of the movie. The movie should be way over three hours, but the output file ends at 2:19, exactly where the first disc ends. Also the movie only has the 22 chapters from the first disc. The 18 or so chapters in the second disc are not there. I believe the output file includes some sort of eof marker from the first disc that is now in the middle of the output file, making the player think thats where the movie ends, How do I merge the two files so the entire movie plays, with the chapters of the 2 parts combined so that what was chapter 1 of the 2nd disc becomes chapter 23 in the merged file? I hope I explained this clearly,

Welcome!

Please read this FAQ entry.

Thank you. After a bit of searching thru the app (Mac), I finally found the menu and settings for appending a file. After a couple failed attempts (wrong settings) I produced a single mkv file of the entire movie with correct running time and chapters