I am not with Laminar Research; just a flight simmer.
One issue with the installation process is to ensure your antivirus software is turned off or deactivated.
The 8GB or RAM you currently have is the minimum requirement. Adding additional RAM will certainly assist with operating speed as X-Plane relies on RAM speed and capacity, processor speed and graphics card speed. You need to talk to your local computer shop for increased RAM capacity. I would suggest a minimum increase to 16 Gb. In doing so however, you need to ensure the RAM chips are exactly the same brand and speed as you will most likely get compatibility issues. Go for at least a mid range chip speed. If your motherboard can utilize DDR4 RAM then go for this rather than DDR3 RAM as this type has a slower upper speed level and has been superseded.
Generally the processor has the ability to be overclocked as the load is increased as well. Overclocking the graphics card also assists when the load increases.
Hope this helps and you are able get a quick resolution to the boot-up speed.