I want to make a side scrolling game similar like this image
How to make a
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Consider looking at the How do I FAQ in the section "Scrolling". You would have some mechanics to implement already which would help you out with your questions.
Also do check videos in the C2 Academy there are likely some mechanics to help out as well.
Consider detailing further more what you are expecting to do. Consider determining what the player is supposed to do, how (what controls scheme) and what impact it does have on your game's world.
As it stands, your question/concept is too vague. How to increment speed ? Add a value to the ScrollSpeed variable you use to make your scrolling.
Here you have a vague answer as well.
As mentioned, the How do I FAQ shows examples of how to make a scrolling (horizontal or vertical).
You can also check the capx examples provided with Construct 2. In your case, the runner example does contain scrolling and "random appearance of obstacles".
This forum has something wonderful called "Search" which, if you use, will allow you to actually answer your questions without having to post a topic for such a treated subject.
https://www.dropbox.com/s/yofoznnody1qy ... e.jpg?dl=0