Hello, sorry for the english,
Das SRF04 hat neben Masse und Vcc noch zwei weitere Anschlüsse, Pulse/SCL und Echo/SDA
The SRF04 is not an I2C device.
If you want to keep to I2C sensors then it would be better to use a SRF08 or SRF10.

Greetings,
H.J. Windt