Hi Jan,
Have you actually tried booting your computer from that USB stick?
By using the dd command to create your bootable USB stick with the Live OS on it the whole USB stick content will be wiped and only the space is used that's necessary to copy the ISO. So you're having a 1GB partition on a 4GB USB stick. The other 3GB are just not used/partitioned.
There is no need to use a larger USB stick.
If you check your USB stick via GUI (disks, gparted) or on the command line (sudo fdisk -l) you will see what I'm talking about.
Hope that helps
Have you actually tried booting your computer from that USB stick?
By using the dd command to create your bootable USB stick with the Live OS on it the whole USB stick content will be wiped and only the space is used that's necessary to copy the ISO. So you're having a 1GB partition on a 4GB USB stick. The other 3GB are just not used/partitioned.
There is no need to use a larger USB stick.
If you check your USB stick via GUI (disks, gparted) or on the command line (sudo fdisk -l) you will see what I'm talking about.
Hope that helps