Search Text, Social Icons and Blog Post Summary question

Hey guys,
so I am new to this theme and not very experienced with wordpress, also.
I have a couple of questions.

1. I want to change the text in the search bar from search, to the german equal, as it is a german site :D. I also would like the text to dissappear once you click on the search bar.
I was kinda able to change the text but not make it dissappear. This is why I changed it back and now I do not know anymore how to change the text either.

2. How do I get those social icons that you also have on your site. I have a plugin that I used with my old site, which is kinda similar but too limited in terms of color. I thought I read there is a plugin/widget included but I can not find it.
I only find the widget “Sparkling Social Widget” which only creates a follow us text.

3. Under settings –> reading settings I setted it to show only a summary of my blog posts, but it still shows the whole page.

I would appreciate your help.
Thanks!