Mid 2009 MacBook startup

have a mid 2009 MacBook that I bought off of eBay. The seller partitioned the HD before selling and I am unable to reinstall El Capitan OS. 

I’ve tried installing through internet Ethernet cable, enter Apple ID/ password, confirm through iPhone then get a ‘try again screen.’

I’m new to Apple products and made a bootable USB with El Capitan installed. I tried downloading it but was met with ‘drive needs 15.98 GB of space to install.’ I tried erasing the hard disk but encounter errors. 

Should I just get an SSD and reinstall an OS?