adaptations of all texts

Hello,
I bought Architect tempate, install it, but now I have big problem...
I thought, that I open text and change it for my text, but in joomla I cant found origin text, in text editor are only some texts not all, not from main page etc... So my questions....
How I can edit all texts?
How can I edit names of pages in template, for exmaple: without Main page it will be xxx?

Iam sorry, Iam total Joomla beginner, thank you for each answer.

Beside articles you have modules , some modules have text in them depending on their type. The most travail case is custom HTML module that infact only shows content. Page names are defend in menu items options. Also check home(default) page menu item PARAMETERS(SYSTEM) because that is special.