Learn Russian: Пицца не сладкая.

The adjective сладкая describes the noun пицца. Because пицца is a feminine noun ending in -а, the adjective must also take the feminine form. For most Russian adjectives, the feminine ending in the dictionary form (nominative case) is -ая.

Why is there no word for 'is' in the Russian sentence?

In Russian, the present tense of the verb 'to be' (am, is, are) is almost always skipped. You simply put the subject and the adjective together. So, saying 'Pizza not sweet' is the natural and correct way to say 'The pizza is not sweet'.

Why is the word не placed where it is?

The negative word не goes directly before the specific word you are negating. Because we want to say the pizza is 'not sweet', не is placed immediately in front of the adjective сладкая.

Is the letter д in сладкая pronounced like a 't'?

Yes! In Russian, a voiced consonant like д changes to its voiceless partner (a 't' sound) when it comes right before a voiceless consonant like к. Because of this pronunciation rule, сладкая sounds more like 'slat-ka-ya' when spoken.