Yes,
Google is (sometimes) your friend, but it's not easy to ask it the right question.
It's possible that the OP has searched for STM32F407
datasheet, and could not find what they were looking for.
STM32 MCUs documentation is usually split over three manuals: reference, programmer, and datasheet.
The
reference manual covers all the registers for each peripheral, with a (bare bone) explanation of how they work and how to set up and use them.
The
datasheet contains a general family and peripherals description, differences between models in the same family, pinouts, and electrical characteristics.
The
programming manual is for core specific information, almost a 1 to 1 rewrite of ARM documentation. It includes also description of ARM core peripherals, e.g. NVIC and SYSCTL.
It's quite a lot, more than 1k pages for for an F4...
To program, in the OP example a timer, include the stmf4xx.h file from the CMSIS, no need for the HAL or LL (the two ST provided abstraction libraries, and where the TIM_OCInitStructure came from), and work your way using the reference manual.
For a beginner with STM32s, it might be easier to have initialization code generated by
Cube-MX, and start from there.