Hello,
1- For this use code given below:
.single-course div#item-header-content .course_excerpt p{
color:yellow !important;
}
.single-course div#item-meta strong:nth-child(2) {
color:yellow !important;
}
.single-course div#item-meta .students {
color:yellow !important;
}
RefeR: https://prnt.sc/ufzv25
2- You can see from here ,, i have no issue on mobile device: https://prnt.sc/ufzvuj
For lock/unlock unit , follow this tip: https://wplms.io/support/knowledge-base/unlock_manually/
Thanks,