Hello,
The bigint issue is because there is no more category, so the "category_left" is consider to be "0" and if you remove 2, you got a negative value (which is a problem when it has to contain only positive values).
You should not delete the core categories.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.