Can anyone help me with what kind of bike this is? This is definitely an old bike, lots of modern work done to it but has original frame. The serial code on it is just under the seat at the back of vertical part. It’s HBK 367 25PC. The front badge simply says ‘bsp made in holland’ And also on the front it says "hand made steel frame"

I’m looking to sell the bike and don’t want to get ripped off.
A quick google search sends one to the Dutch bike manufacturer BSP: https://www.bsp-fietsen.nl

According to what the internet says it's a Dutch family company started in 1986. They build their bikes in the Netherlands, according to what their webpage says.

As it comes to the geometry of your bike it's the typical Dutch "oma fiets" - grandma bike. I wouldn't be surprised if the bottom bracket was a threadless press-in style.