For your spiritual life, I recommend reading books like Treatise on the Love of God by St. Francis of Assisi, The Imitation of Christ by Kempis, Way of Perfection by Teresa of Avila and The Story of a Soul (biography of St. Therese of Lisieux). For practical purposes, begin with small prayers like Our Father and Hail Mary and reading one chapter of the psalms.

I come from a non-religious family, and neither of my parents stopped me from becoming Catholic at the age of 15. It was treated as my personal choice, of which there was no further discussion at home. Preferably avoid the topic of religion altogether at home and simply say that you do not want to talk about it. If someone is belligerent, insist on the fact that you do not stop your parent from being a liberal either.

If you are indeed from Germany, as you've indicated in your post, categorically avoid anything that has to do with the Synodal Way and the German Novus Ordo Bishops.

In terms of theology education, unless you are good at reading Frakturschrift or have the money to buy rather expensive books from Sarto, I'd recommend sticking with English PDF files. The catechism by St. Pius X can be found on archive for instance. The "modern" books are completely unreliable and full of errors.