what is the best opening in practice?

what is the best opening in practice? i am a 850 elo player an ive used many openings all were good but what is the best opening for newer players as my friend is new to chess and wants to learn a good chess opening to win most games with

Anything 1.E4 is good for beginners

In general, the best opening is one that:

1) You know better than your opponent, and

2) Leads to positions in which you are comfortable.

1. e4 openings tend to be fairly intuitive, although you may feel the need to study a few lines to avoid being trapped by a more knowledgeable opponent. The Scotch Game is probably the simplest to just jump right in

1. d4 openings are generally much safer as your center has better support, you aren't inviting an early affack on f2, and your opponent is less likely to have studied it as much. Queen's Gambit and London are both solid systems that are playable at your level without a lot of study.

Beyond that, all the "standard" openings are pretty much equal as long as you play them propely. Pick an opening that looks attactive and give it some study (which doesn't mean just memorizing lines. Understand the *why*)

Depends on your goals. Playing for fun? Many gambitos are perfect. What something more "practical"? Italian is very playable and can be a good one.

At your rating you don't want to be bogging yourself down with opening theory. Focus on principled opening play, just google that. Then get really good at tactics.