Saying hello

There is a long-running thread where you could introduce yourself.

There’s a FAQ thing at the top but you seem to be doing pretty well so far.

SketchUp is not AutoCAD. Probably the best thing you can do for yourself is get past that. They work differently. You’ll just frustrate yourself trying to make SketchUp work like AutoCAD.

There are ways to do those sorts of things both with native tools (as has been described) and there are some extensins out there that can add functionality along these lines. Frankly, the only time I ever need to trim or extend lines is when I have to work with bad CAD files from other people. I don’t have any problem avoiding them when I am creating my own models in SketchUp. Usually when I get CAD files like that I just start over and model the thing myself because there are usually so many issues, it takes more time to fix the garbage than to start from the beginning.