You can't objectively measure your speed as a developer. Attempts to try and measure developers' speeds will cause perverse behaviors - like rushing code to get it checked in quickly and making things less generic, splitting up bugs (so more bugs are fixed per month) etc. And this would cause those developers to actually slow down in terms of business value delivered.

Don't worry about speed, focus on effectiveness.

The trial and error thing - next time see if people can help you either in your team or getting answers online etc. That may reduce the time spent in trial and error but sometimes it is unavoidable.