Formatting problem of text on the blog

Hello,
I am always looking for help to create rticles of my blog.
My problèle lies in the fact that the text of the content extends beyond the text box and continue straight on the background. Without replacement line …
It’s the same , whether the articles and pages on the blog page.
I tried to vary the blog templates (blog/blog grid/blog small), but the bug is the same.
Have you brought me a solution ?
thank you.