Every child has her own rate of growth and development. While it is true that kids pick up languages when they are young, having exposure to many languages at once too can delay speech in some kids. It may be that while they understand everything, they may not be able to find the right words to express. With regards autism, they are other concerns that need to be evaluated by an expert.
Next Steps
You can consult a child development expert and get proper evaluation done. You can also consult for Homeopathy along with child diet and routine to promote child development. Autism can be evaluated by doctors and homeopathy too considers the behaviour patterns and prescribes medicines.
Health Tips
Try sticking to one language for sometime and encourage your baby to speak and interact in form of words. Avoid rushing to conclusions, as such behaviours are common and can be dealt with proper consultation.