how to make a nice front end for a website

hi i am a student i am really very much interested in making a website , my backend is good and i can use templates and make websites , but i really wanna be a full stack website developer , i can not make any website with my front end skills , i have followed up a lot of tutorials on youtube , and other courses but none provides the way to make a good template like i know about media query in css i can use it , its pretty much easy and i know about bootstrap too ..

what i need to know is how can i start building a nice template which works on mobile as well because as far as i have seen, there are 3 main components which are :

1: header 2: main content 3: footer

so can anyone suggest ? how to make these three components perfect ? should i use the grid system in bootstrap ? and if i do whenever i make the browser's length short it wouldn't work the way i want ? means it wouldn't show up accordingly on what width i want .

please assume that i do not know anything of making these components and guide me a bit ? thanks because taking courses and visiting w3school is not a problem the main thing i am trying to focus on are these 3 components .

Also please if anyone could guide me for the admin panel as well ? from where i can learn making that but i tell you i always face these problems when making anything i get too much confused