To make individual notes longer you would have to edit the MIDI notes themselves in the Piano Roll [as you apparently did]. Changing the length of the Regions above will not affect the lengths of the individual notes inside those Regions.
But it doesn't matter how long a MIDI note is, if the instrument on that track plays only short notes, then it doesn't matter how long the MIDI note is, the actual audio note that you hear will stop when it's over. An electric piano is like that -- it doesn't matter how long you hold the note down, the actual audio note will play for a second or two and then fade out, even if you're still holding down the key [or even if you extend the note length in the Piano Roll, as you did]. Only instruments that play sustaining notes -- notes that can last as long as you hold down the key, or for the full length of the MIDI note -- will behave the way you're expecting. An example of that would be, say, an organ, or strings [but NOT pianos, or bass, or guitars] -- try different instruments and when you find one that can play longer notes and hold those notes indefinitely, then you can play or edit the MIDI notes [as you did] to make the notes last as long as you want.