i dont want to show full post

https://codex.www.ads-software.com/Customizing_the_Read_More

don’t edit Twenty Eleven directly – create a child theme https://codex.www.ads-software.com/Child_Themes to make the edit in there.
it is important to have an unedited default theme Twenty Eleven in case of problems. also, direct edits to Twenty Eleven will be overwritten with the next upgrade of your wordpess version, customisations will be lost.

once the child theme is in place, you should be able to get specific suggestions on how to solve your problem.