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Welcome to the TAC community Ana! Simple matters to correct.
Proper choice of a pick is whatever works best for you. Typically with flatpicking, a more firm pick is used, and with strumming (especially a beginner), a less firm pick is desired. Play around with different picks and choose whichever has the better feel and allows you to play the most efficiently and easiest way.
As for correct posture, holding the guitar, etc., everyone looks at their guitar when beginning, and there is nothing wrong with it. As you become more accomplished, you won’t need to look as often, because you’ll have built up muscle memory in your hands, and they’ll automatically go where they are meant to. Even experienced players peek at their hands occasionally. Ideally, you’ll want to try and have the best posture and positioning of your guitar to avoid fatigue and injury of any kind over time. And good posture leads to cleaner playing. But for now, just do what you need to do to play the guitar.
Hope you have lots of fun with it!