Help editing the theme code

Hello.

Earlier, I was told on this page https://ww.wp.xz.cn/support/topic/lifestyle-theme-has-an-issue?replies=2, that there was an error with this theme that needed correction if I wanted a particular plugin to work. he error is simply just a line of code. I was told that it would be resolved. However, it hasn’t yet. I was just wondering if this code could be fixed or if there is a way to do it myself, as I urgently need this particular theme.

Please, thank you.