Previously great advice: Don’t feel unwelcomed, ever. God will never turn you away so long as you always believe.
Most of what we Catholics believe will be contained in that short Mass. The sitting , standing and kneeling all have significance. We all do it together, there’s a unity we share, not just with the Blessed Trinity, but with each other, in prayer, belief and faith.
Much of what we believe you will read in the Nicene Creed. This will follow the Priests Homily, which is somewhat similar to your sermons. The Homily puts emphasis on the Gospel reading and the meaning and messages of the days Gospel as it relates to our lives today. Read the Creed, it goes way way back, to the 4th century at the Counsil of Nicaea.
Notice that yes, we Catholics do read the Bible, amazing

There will usually be 2 readings, 1 from the Old Testament, 1 from the New, and the Gospel that will be read by the Priest. The Gospel we stand, and we give special reverence. The Word of the Lord is above all and deserves the extra reverence.
The high point of the Mass will be the Holy Eucharist. We listen to what Jesus commanded us to do. Eat his flesh , drink his blood. When we Catholics receive Holy Communion, we become part of the Body of Christ, Again, unified in faith, beliefs, in how we conduct ourselves to reject sin so that we’re worthy of receiving what makes us part of Christ, and the Church he left us. Imagine the millions and millions around the world who are taking part just so we are one with Christ, imagine one day you’ll be part of that, I think that’s awesome
Hope your experience leads you closer to God. That’s what attending Mass is all about. To give thanks to God for our blessings, and to acknowledge what Jesus sacrificed so we could enjoy those very blessings.