Reading a high rate (400 kHz) analog input with an ESP32 (or Arduino)
Your sensor uses an I\$^2\$C interface with a clock frequency of 400kHz. The actual conversion rate of the analog signal is much slower than that, but in any event you will receive your data through a digital I\$^2\$C connection rather than by digitizing an analog input.

If I understand the datasheet correctly, you must transmit the slave address and a register address, then the sensor responds with a 16-bit value for one channel of the input. That's going to take at least 36 clock cycles. Optimistically, you might be able to read register values at around 10kHz.

However, looking at the ALS_MEAS_RATE parameter it appears that the sensor requires 50ms to do an analog-to-digital conversion, so your fastest sampling rate is actually 20 samples per second.