How long will it take to master lightroom without basic knowledge? I am a late photographer. Is it necessary to learn?

This is not necessarily the case, it varies from person to person, and it varies according to the time of learning to use the software.

As long as you like it, you will learn faster, and success is inseparable from hard work.

I suggest you go to the self-study website to study the basic course of Lightroom6.

"Lightroom6 Basic Course" is divided into * * chapters 1 1, which includes novice Lightroom going on the road, putting photos into computers and software, viewing photos with the gallery module, managing photos in its own way, modifying the module of photos, basic correction of photos, preliminary mastery of Raw format, color trimming, noise reduction and sharpening and local processing of photos, wonderful use of various artistic effects, and so on.