I'll help you with the summary. Breaking it out below:
a young man died after saving a unique species of Draco from a fanatical devotee of the Tiamat cult. he did not expect to wake up in a borderless white room in front of a mighty dragon.
A sentence begins with a capital. "A young man... He did not..."
MC can travel across multiverse
first world MCU
What is 'MC' and 'MCU'? In a summary, these need to be spelt out even if you can rely on assuming a reader understands what these mean.
i don't have any right regard the novel
So a translation? Best not to put this on the summary add it to an auxiliary chapter instead with a lot of other disclaimer/explanation details.
In general. This summary is vague and doesn't tell me a lot about what the story is really about.
A man find's himself meeting a dragon in a borderless room after dying. If this is all I need to know about the story, then it's not going to attract interest from me. As a reader, I want to know what I'm going to get out of this book. Am I going to be in for some action, adventure, fantasy, a gunfight...?
Show the reader this story has more to expect than just a guy meeting a dragon. You need to do this in your summary and preferably under 750 words (normal word count for a paperback back-cover before fonts start to blur). Every word must count to convince a potential reader that your book is worthy to be read.