Regarding Tables, Rules and Header

[bitterlord]

I have been trying to change some things on my theme and had some problems regarding that. First of all

I cant change the colors of the TABLE's, and it looks bad since it's background merges with background of the site itself (I don't know coding jargon, sorry). The code I am using for this is:

table {
border-collapse: collapse;
width: 50%;
width: auto;
min-width: 65%;
margin: 0 auto;
}

table th, td {
border: 1px solid #ffffff;
}

table th {
color: #0e0e0e;
background-color:#fedd59;
background-image: url('https://cdn.discordapp.com/attachments/1117902933594492998/1134557994126946374/bd48da_02456bfba66a4022b40985bc3c89375fmv2.png');
background-clip: text;
background-size: 25%;
font-weight: 700;
font-family: var(--title-font);
text-transform: uppercase;
}

Second problem is with Rules, I dont know which code edits them, can you help about it?

It doesn't suit with my pursuit of modernising the site

Third is regarding the Header, how can I get rid of the outer black line

Thanks in advance