> do indexes pose risks on performances?
They improve query performance where they can be used. They can slow down Inserts & Updates.
> could it be fatal if not uses correctly?
?! I never heard of anything or anybody dying from an index.
> how could I know If I do wrong or not on my index add choice?
Much to read, eg
https://www.slideshare.net/myxplain/mysql-indexing-best-practices-for-mysql
> should I add more indexes depending on other queries I do in record table?
If there are queries on the table that are underperforming, probably.
> how do you find my record table structure and volume of data? is it normal?
> `id` bigint
Really, you expect 9,223,372,036,854,775,807 rows? Int unsigned would give you 4.3 billion, wouldn't that be enough?
> `details` longtext,
You need 4.3 billion text bytes per row?