I need to work on a logo animation, it's just letters with the google font "Josefin Sans". I have this glitch, i tried with more resolution preview samples, to change the offset, but it's still buggy. Can someone help please ? Thanks
TTF fonts are a bit buggy in Blender. You have two options.
Use another font. OTF fonts work better in Blender. This is a good option if you have a lot of text
Or convert the text to mesh and merge misplaced vertices manually. This is good if you have only a little bit text. You can convert text to mesh in Object Mode from Object menu under Convert To and by selecting Mesh from Curve/Meta/Surf/Text.
You can merge vertices in Edit Mode by selecting the vertices you wish to merge and by pressing m. This will give you options of how you want to merge them. In this case Merge At Center seems like a good option.
After this you can select vertices and press f key to fill missing faces. 4 vertices at once should be fine.