The only computer I see associated with that motherboard is the Lenovo ThinkCenter M72e. It comes in 3 form factors: tower, small form factor and tiny. The tower and small form factor have 2 RAM slots and can support up to 16GB of total RAM. The tiny uses SODIMM (laptop memory).
Is your computer the Lenovo Thinkcenter M72e? I think MAHOBAY NO DPK is the motherboard, not the Lenovo Model. Is it the desktop tower in the link I gave above? We need to know exactly what you currently have so we know what upgrades are compatible.
After a minute or so an option to chat with someone will pop up. You may want to tell them your exact model and are looking for specifications (CPU's supported, RAM supported, Graphics cards supported, etc.) Maybe they have archived documents somewhere. My guess is you are going to be limited to third generation processors.
Maybe someone else here is more familiar with the H520 desktops and can help out.