Rom 14:5 One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind.
For those who believe that Saturday(the Sabath) is more important, then for them it is . For those who believe Sunday(the firt day of the week) is more holy ,then for them it is.
The Sabbath ( day of rest) was made for man ,not man made for the day.
Mar 2:27 And he said unto them,
The sabbath was made for man, and not man for the sabbath:
OT law requires rest on the seventh day (Saturday) by the modern Calender.
However, as some have stated, that was a shadow of the coming rest found in Christ Jesus. No one is bound by this doctrine/ law except those who choose to bind themselves to it. And they have no business trying to bind others by their beliefs.
While many disciples "being Jews" entered the temple on the Sabbath (Saturday)they and the gentiles "the church" were acustomed to meeting the first day of the week(Sunday).
Act 20:7 And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
1Co 16:2 Upon the first day of the week let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come.
BTW "You Tube" is not a reliable source of biblical truth. May I suggest that you stick closer to the Christian faith and limit your resources to scripture and Holy Spirit guidence.
It will save you from a lot of needless and dangerous confussion and worry in the future.
Respectfully
Cliff