If you wish to remove Tasks to Complete block from the Dashboard page then please add the following CSS code in Edwiser RemUI settings inside Custom CSS section Tab.

/* Remove Task to Complete Block START */
@media only screen and (min-width: 780px) {
.block.block_myoverview #new-course-stats {
padding-right: 1.715rem;
padding-left: 1.715rem;
padding-bottom: 1.715rem;
width: 100%;
}

.block.block_myoverview #new-course-stats .panel-body .counter-label {
padding-bottom: 1rem;
}

.block.block_myoverview #new-course-stats .panel-body {
padding-right: 4rem;
padding-left: 4rem;
}
}
.block.block_myoverview #new-upcoming-block {
display: none;
}
/* Remove Task to Complete Block END */