Apart from one minor mistake for hydrogen it looks OK to me.
we calculate the atomic mass by adding the protons and the neutrons multiplying it by 1 amu
is not entirely true. What you get adding number of protons and neutrons is the atomic mass number
(AKA nucleon number or mass number). It tells you how many nucleons are in the nucleon, but the mass of the nucleus is a bit lower than the sum of the masses of nucleons (so called mass deficit). As most elements in the nature are mixtures of isotopes atomic mass is a bit different, and is a weighted average of all isotopes present.