How to resize boot partition
Solution 1:
You shouldn't have to repartition the disk just to reinstall Ubuntu. It seems like you just have one partition for Ubuntu, and one Swap partition in an extended partition, which is a standard partitioning scheme for an Ubuntu installation.
You could boot the Ubuntu iso from the Grub menu. When you boot from the iso file, you will be able to press a key upon boot to get to the Live boot menu. Add the toram
kernel option.
You will be able to choose whether you want to save programs or Home folder data or just erase everything and reinstall.
And importantly, make reliable backup before executing the procedure! Though nothing should go wrong if you ensure that you know what you're doing.