After the esophagus which comes next in the alimentary canal

The food bolus will then get digested in the stomach.

Specifically, only protein is chemically digested into short polypeptides under the enzyme pepsin. The gastric juice that contains pepsin is produced by the gastric glands. The stomach is very acidic. It has a pH value of around 2. This is because it has to make sure that only pepsin is functional and so as because hydrochloric acid is present.

Polypeptides are not yet the final form of protein, amino acids are. But the process of breaking down polypeptides into amino acid is yet to be done at this stage, so as the other digestion of e. g. carbohydrates or fat. They'll mostly be done in the duodenum, which is the next stage after the stomach.