Statement-1: The decreasing order of acidic character of ${\mathrm{CO}}_2,{\mathrm{N}}_2{\mathrm{O}}_5,{\mathrm{SiO}}_2$ and ${\mathrm{SO}}_3$ is ${\mathrm{SO}}_3>{\mathrm{N}}_2{\mathrm{O}}_5>{\mathrm{CO}}_2>{\mathrm{SiO}}_2$

Statement-2: Oxides of the metals are generally basic and oxides of the non-metals are acidic.

It's a true statement. The nonmetallic nature of oxides changes over time, which changes how acidic they are. On the other side, as the group gets smaller, the metallic character gets stronger, which results in a decrease in the acidic nature of oxides. Therefore, $S{O}_3>{\mathrm{N}}_2{\mathrm{O}}_5>{\mathrm{CO}}_2>{\mathrm{SiO}}_2$ is the correct order of the acidic character.
​It is a false statement. In the modern periodic table, the acidity of oxides increases when travelling from left to right in a period and decreases when moving from top to bottom in a group.