Delete Mac partition and grow Ext4 partition

I have a 2015 non-retina Macbook pro with a dual boot Mac-Kubuntu 18.04. I installed initially Mac Mojave (APFS File system), then rEFInd from there and finally Kubuntu. This is how the layout looks like:

Basically, I would like to delete partition number 2 (MAC apfs) and grow the existing Kubuntu partiton (number3) so that it takes the whole space.Is there a fairly safe way of doing this? This is a more detailed view of the partition layout:

Thanks in advance for your help!