I'm having trouble positioning the box I created with Tikz on the left of teh page. I tried making it a floating figure too but nothing.
#Tikz can't be placed on the left of the paper
high magnet
Not a direct answer to your question. Imho, if you're not already quite familiar with latex, you'll be better of doing this with a more user friendly “wysiwyg” (what you see is what you get) tool. Making a poster with latex is possible of course, but it's quite involved, and far from a beginner friendly task.
lusty root
Not a direct answer to your question. Imho, if you're not already quite familiar...
I can write my own documents just fine with LaTeX, making significant changes to hwo things look is however new to me. I got aroudn the problem thou with a mix of minipages and jsut removing margins.
Doing this is pretty new to me. The goal here to is to automate making instagram posters for where I work. That's why I'm doing this.
high magnet
I see 
. If you're going to place everything on a single page, and use absolute positioning, then I'd recommend you put everything in an absolute positioned TikZ picture... The code below might help you get started?
\documentclass{article}
\usepackage{tikzducks}
\usepackage{anyfontsize}
\usepackage{graphicx}
\usepackage{geometry}
\usepackage{tikz}
\usepackage{xcolor}
\geometry{paperwidth=30cm, paperheight=30cm, textwidth= 20cm, textheight= 20cm, margin=5cm}
\definecolor{boxCyan}{HTML}{0E9E75}
\pagestyle{empty}
\begin{document}
\begin{tikzpicture}[remember picture, overlay]
\node at (current page.center) {\includegraphics[width=\paperwidth]{example-image-duck}};
\node[
xshift=3cm,
yshift=-3cm,
opacity=0.8,
text opacity=1.0,
font=\fontsize{24}{13.5}\selectfont
] at (current page.north west)
[text width=7cm, fill=boxCyan, above right]
{%
Text%
};
\end{tikzpicture}
\end{document}
The PGF-TikZ manual has some helpful insight and example in section 17.13 “Referencing Nodes Outside the Current Picture”, especially keys /tikz/remember picture and /tikz/overlay should be relevant for you.
I would avoid using \sections if you're not going to use this logical structure (nothing prevents you from defining commands to apply a consistent style, of course, such as e.g. \myHeadingFont that should expand to \settextfont{Some Font}\fontsize{50}{12}\selectfont or whatever you prefer).
Hopefully this is enough to get you started!