Change the Bold Text in Math Mode to Normal

Question

I have an issue in a quite large document i have with Latex. I am writing a lot in math mode, especially with align function, but the output always turns out bold!I do not wish that all text I write in math mode gets this new bold look, and I do not know why it started doing that. I want the math output to be the "usual", I will post a picture of how the output looks vs how it should be.

This is my current font of my output:

This is my desired font of the output (don't look at the content)

Its quite hard to show the code as I have a rather large document with several files and inputs, but I am putting in the main code below, and the section of the math mode.

The section with code ( it is in the file called 3.tex which is an input in the mainsheet.

\section{Model}
\begin{align*}
\frac{dV}{dt} = e^TF \\
\frac{dn}{dt} = C_{in}F + RV
\end{align*}

My Main Sheet with all initialisation

\documentclass[a4paper,11pt]{article} %type document
\usepackage[utf8]{inputenc}
\linespread{1.15} %linjeafstand
\usepackage{graphicx}
\usepackage[english]{babel}
\usepackage{fancyhdr}
\usepackage{svg}
\usepackage[margin=1.5in]{geometry}  % For margin alignment
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{algorithm} %a lgorithms
\usepackage{arevmath}  % For math symbols
\usepackage[noend]{algpseudocode} %algorithms
\usepackage{graphicx} % bilder
\usepackage{geometry} % layout
\usepackage{float}
\usepackage[hidelinks]{hyperref}
\usepackage[demo]{graphicx}
\usepackage{caption}
\usepackage{subcaption}
\usepackage[nottoc]{tocbibind} %Adds "References" to the table of contents
\usepackage{caption}
\usepackage[justification=centering]{caption}
\usepackage{biblatex}
\addbibresource{sample.bib}
\usepackage{amsmath}
\usepackage{gensymb}
\usepackage{verbatim} 
% giver flere muligheder til at lave nummererede lister
\usepackage{enumitem}
\usepackage{xcolor}
\usepackage{url}
\usepackage{textcomp}
\usepackage{pdfpages}
\usepackage{endnotes} 
\usepackage[most]{tcolorbox}

\setlength{\parindent}{0pt}
\geometry{top=2.5cm, bottom=1.5cm, left=2.5cm, right=2.5cm}
\pagestyle{fancy}
\fancyhf{}
\lhead{Bachelor Thesis}

\usepackage{lastpage}
\fancyfoot[c]{Page \thepage \ of\ \pageref{LastPage}}
\renewcommand{\headrulewidth}{2pt}

\title{Bachelor Thesis}
\date{\today}

%Includes "References" in the table of contents
\usepackage[nottoc]{tocbibind}

\begin{document}
\hbadness=100000
\vbadness=100000

% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %%%%%%%% Sections with roman numbers %%%%%%%% 
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\fancyfoot[c]{Page \thepage}
\pagenumbering{Roman}
    \input{sections/00.tex}
    \pagebreak
    \setcounter{secnumdepth}{4}
  %  \tableofcontents \pagebreak
\fancyfoot[c]{Page \thepage \ of\ \pageref{LastPage}}
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %%%%%%%% Sections with arabic numbers %%%%%%%% 
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    \pagenumbering{arabic}
    \tableofcontents\thispagestyle{empty}
    \input{sections/0}
    \newpage
    \input{sections/1}
    \newpage
    \input{sections/2}
    \newpage
    \input{sections/3}
    \newpage
    \input{sections/4}
    \newpage
    \input{sections/5}
    \newpage
    \input{sections/6}
    \newpage

\end{document}

Answer 1

Do you like to have only math fonts in sans serif? From second showed image can be concluded, that all document should be in sheriff font:

\documentclass[a4paper,11pt]{article} 
\usepackage{geometry} % layout
\linespread{1.15}

% sans serif math font? If yes, uncomment one of the next packages
%\usepackage{arevmath}  % For math symbols
%\usepackage{sfmath}     % try it instead above

\usepackage{amsmath}
% for showed equation
\usepackage[version=4]{mhchem}
\usepackage{siunitx}

\usepackage{lipsum}

\begin{document}
\section{Model}
    \begin{align*}
\frac{dV}{dt} & = e^TF \\
\frac{dn}{dt} & = C_{in}F + RV
    \end{align*}
\lipsum[66]
    \[
\mathrm{NIP} = \frac{\qty{-6.94}{\kilogram}\text{ \ce{CO2}-eq}}
                    {\qty{8400}{\kilogram}\ \ce{CO2}/\text{-eq/person/year}}
             = -0.00083 \text{ pr. person/year}
    \]
\end{document}

In the case, that math should use sans sheriff fonts, the font selected by arevmath package cause (as already mentioned mentioned @dalef in his comment, a bit thicker fonts. For thinner font you need to change used math font, for example with sfmath: