Is there any website providing script from mangas in textual format, so that I could just paste it in Google Translator? There are so many Chinese mangas that I cannot read, and it's to hard for me to rewrite the signs into Google Translator by finger.
There is not a page that I know of that stores the text version of manga, actually I'm not sure such a page would be legal considering the huge legal struggle over lyric sites in the past. However, what you are asking is not impossible.
There is a technology called optical character recognition (OCR) which is software scanners use to generate text versions of the scanned document. There are several programs that implement this technology for use in translation software. Some are available as apps available on your phone and can be found in the app store for your device. While there are many implementations available, one such implementation called Capture2Text uses OCR specifically for the use of translating manga, visual novels, and so forth.
These programs will copy the characters to your clipboard which you can then put into your favorite translator. There are also some programs available out there that will search multiple translators at once or even allow you to create your own dictionary of words to look up words/phrases in.