When im trying to format my HDD, im getting an "Can`t mount ext4 type" OR "Cant fr4omat" type errors. My HDD works fine while under Windows.
Are you trying to install Ubuntu MATE alongside Windows or do you want to permanently replace Windows?
Do you have only one drive in your system?
Is your HDD tiny or small (2 TB or less), or is it larger?
Do you want to boot with msdos BIOS or UEFI?
Does your HDD have a Master Boot Record (MBR) or a GUID Partition Table (GPT)?
What program are you using to try and format the HDD? If it is the installer the name is probably Ubiquity.
Did you choose "Something else" during installation?
Most likely your blocksize is incorrect - values like 1024, 2048 and 4096 when creating a new ext4 filesystem - if the blocksize is larger then 4096 ext4 does not support that
mkfs.ext4 -b 4096 /dev/sda1 - where sda1 is your external it may be different