Greetings,
Welcome to the forum.
I am not a HP employee.
You have upgrade options. But what do you want to improve; gaming, system responsiveness? Do you have a budget?
The best upgrade to improve your general PC experience is to upgrade from a platter HDD to a SATA SSD.
You would need to upgrade the graphics card if you want to do 4K gaming at decent FPS. You would also have to upgrade the current 180 watt PSU to at least a 500 watt PSU if you upgrade to a Nvidia 1070 or a 1080.
You can go from the current 8 Gb of RAM to 16 GB of RAM.
You can upgrade the processor to a i7-7700.
Upgrading the graphics card requires measuring along the PCIe x16 slot to see how long the card can be and if a dual slot card will fit. The chassis may be the limiting factor. You would also have to measure the existing uATX PSU. Then shop for a similarly sized PSU with the required watts and supplemental PCIe power connectors to run the new graphics card.
Upgrading the graphics card and the CPU may require upgrades to the currently installed cooling systems (chassis and CPU).
You would have to decide where you want to start based on your specific needs and your budget.
Regards