I`ve been playing trombone for 1.5 years and i feel like expanding myself. Would it be safer to perfect myself in trombone first?

Think of doubling as cross training in sports. If done properly, I doubt you will damage your trombone playing, but since your practice time is divided up, you may not progress as fast.

The big thing to remember, when you are tired STOP! I have seen way to many embouchers messed up from over playing.

My question is why do you want to play other instruments? Sure, it may be necessary if you are playing in a polka band to double on trumpet and fluegal horn. You are playing the most perfect instrument in the world. Perfect yourself with it.

I think you should stck with what you are doing now. When you have play for 4 or 5 years; you`ll know enough about what you`re doing to make a change and not lose your ability to play trombone.

then i shall stick with trombone until i master it, thank you for your wisdoms

You ought to borrow a trumpet from your fellow band members and give it a try to see what happens for you. You don`t need to learn how to play it, just keep all the valves up and toot around on it. It won`t hurt your embrochure to experiment. I know several trombone players that also play trumpet, cornet, or marching french horn and say that it allows them to build a better embrochure all around. If you are comfortable with it you may find other brasswind instruments that intrugue you and play more than one type. This flexibility might allow you to be more creative in a way that is comfortable to you. Or, you may want to choose one instrument and settle into it.