At this age, it's possible that your child might start behaving differently when he's outside home. Children are most comfortable in their home turf and display a different level of confidence than when they are taken to a different environment. For any kind of learning to be successful it is first important for the learner to feel comfortable in the particular environment, and that is what your home will do for your child.
What you can do
It is a good time to introduce play dates to him. Children at this age start becoming more co-operative, sharing, and talkative, and start showing leadership qualities. In the company of children their age, your little one might feel more confident and accepted. This would give him a free will to talk and share his creative ideas, thereby enhancing his imaginative skills. It's also a good way for him to add a lot of new words to his vocabulary. After a fun play date your child might also like to excitedly share everything that they did. This would again create an opportunity to practice speech and language.
When it comes to play dates, try to organise as many at home. By calling children of the same age for a play date, you will give your child ample opportunity to practice their language and speech skills without feeling shy.
Life's always more fun if you play games and for children play is serious learning!