I don’t want to install grub - it is always source of 90% of my problems (but it’s my fault, because of the sharing /boot partiton) and also syslinux is much easier to configurate, so I’ll stick with syslinux
so thank for answers, this can be marked as answered, because I found out that:
from one syslinux (located in /dev/sda1) I can chainload syslinux located on another partition (that @manuel guided me to create it: /dev/sda4/boot/).
So I need to install syslinux on the other boot (/dev/sda4/boot) partition and there have a config that says: “boot this kernel from this partition”. … I don’t know why I just can’t have in the first syslinux (/dev/sda1) something that says: “boot kernel from /dev/sda4/boot” life would be much easier but instead, you need to have a kernel in same partition as syslinux
But I decided to properly repartition my HDD (since as you see on my first post, I get these errors:
Partition 2 does not start on physical sector boundary. Partition 3 does not start on physical sector boundary. Partition 4 does not start on physical sector boundary.
and install fresh antergos.
thank you guys