It looks like /dev/sda1 has 58 available gigs.
In order to perform the action, You must boot into a LiveUSB and have the /dev/sda drive unmounted.
Once you are booted into LiveUSB and ensured that /dev/sda is unmounted (you can usually just mount or unmount the volume in your file manager), launch Gparted and on the /dev/sda1 partition, click it to select it, then click the delete partition button which looks like a minus sign (-)
The /dev/sda1 partition should show as free space. You can then right click the /boot partition /dev/sda4 and select resize and use the slider to resize it into that available free space.