This is not really a problem.
If a large company does something similar, it does not mean that they will do better. Well, this does not mean that you should rely only on technology, in order to occupy your niche and win in the possible competition, you need to have as many customers as possible ready to use your product.
From my own experience, I can say that this is terribly offensive, but in fact for the best.
First you need to get used to the idea that you are not the only one who has such an idea. There are 7 billion of us on earth. Therefore, if you have thought of something, then such a thought must have crossed the mind of someone else. And it is quite possible that there are hundreds of such people. And only a few begin to really realize their idea.
Of course, at the initial stage, the one with the best funding will get ahead. But in business (and that is why you created your startup) being second is not a bad thing at all. I can honestly say that it is even better.
The leader goes by trial and error. Spends disproportionate resources on it. You can (and now you really must if you want to survive) watch him. Use some of his ideas to improve your product. Consider his mistakes. This will allow you to spend less resources and time to achieve similar results.
And yes, the competition is pushing you to be more active. And based on the result of your competition, the final product will only benefit the consumer.
Not enough input data to answer your question. What kind of startup - services, production, trade? What is the size of the market you are interested in? At what stage is your project? How much have you invested in it and are still ready to invest? What methods of promotion did you plan to use?
The appearance of a major player on the market is not a tragedy in itself. But a specific answer needs specifics.