You have some type of hardware problem. Could be heat or some physical hardware is faulty.
IIRC the 2008 and early 2009 MBPs had faulty hard drive to logic board cables. Worked sometime with some files then with other files it didn't work. Worked with slower rotating HDD and didn't work with faster Solid State Drives (SSDs).
Then you have the Faulty GPU chips that affected all 2008 models and continued into some models 201x models.
Right with the Vintage Mac and that older version of OS X you can't run newer versions of a lot of software. This is because Apple changed the OS and software writers had to Keep Up to what Apple was doing which stopped that newer software from working on older version of OS X.
It might be time to get a new, or newer, computer.
How can I know for certain what the osx it has?
Click the Apple menu in the upper-left corner of your screen and select About This Mac. That will list the marketer's name of your Macos version (e.g. Mavericks), the version number (e.g. 10.9.2), and the hardware model (e.g. Macbook Pro late 2009). Please post here exactly what you see, or better, a screenshot.
10.9 is "Mavericks", which is four years old: macOS - Wikipedia
Most likely you have a MacBook Pro (Mid 2009): MacBook Pro (15-inch, Mid 2009) and (15-inch, 2.53 GHz, Mid 2009) - Technical Specifications
(Until relatively recently, Apple traditionally made it hard to figure out which model of hardware and version of software you have. Recent versions of Macos just tell you explicitly.)
LR Classic (LR 7, the desktop version of LR) requires Macos 10.11 (El Capitan) or later: Lightroom Classic CC system requirements .
Your Macbook Pro (mid 2009) can run Macos 10.11 (El Capitan): OS X El Capitan - Technical Specifications . But it can't run Macos 10.12 (Sierra) : MacOS Sierra - Technical Specifications nor Macos 10.13 (High Sierra): MacOS Sierra - Technical Specifications .