Hi Tzeunis,
according to your issue, there might be problems with motherboard, RAM, cable, case bottom or power supply
it's hard to distinguish which one is failed
If there is a start bottom (red one) on your motherboard, you can try to start computer with it (shown as following picture)
If it is still not working, then I will suggest you check all these components one-by-one or you can find the retailer to check for you