Q: Drawing 3D diagrams in LaTeX I'm currently writing my bachelor's thesis and I'm having trouble with 3D diagrams. Up until now, I was using Inkscape but I was not satisfied with the look of it. Especially with the look of the arrows. I would be very happy if someone has any suggestions as to what application I should use.
That's what I want my diagrams to look like:

I have also tried TikZ, but it takes too much time.

A: Drawing the figure with TikZ does not take too long. Maybe it does for TikZ new users, but it is time well invested because in the long run you will be able to make drawings like this in a short time.
For example, the 3d part would be something like this, using isometric perspective:
\documentclass[tikz,border=2mm]{standalone}
\usetikzlibrary{3d}                   % for canvas is... options
\usetikzlibrary{decorations.markings} % for arrows at midpath

% isometric perspective
\pgfmathsetmacro\xx{1/sqrt(2)}
\pgfmathsetmacro\xy{1/sqrt(6)}
\pgfmathsetmacro\zz{sqrt(2/3)}
\tikzset
{%
  isometric/.style={x={(-\xx cm,-\xy cm)},y={(\xx cm,-\xy cm)},z={(0cm,\zz cm)}},
% arrows
  my arrow/.style 2 args={decoration={markings,mark=at position #1 with
                          {\node[right] {$#2$}; \arrow{stealth}}},                                          
                          postaction={decorate}},
}

\begin{document}
\begin{tikzpicture}[isometric,scale=2]
% axes
\draw[dashed] (0,0,0) -- (1,0,0) coordinate (X);
\draw[dashed] (0,0,0) -- (0,1,0) coordinate (Y);
\draw[dashed] (0,0,0) -- (0,0,1) coordinate (Z);
\draw[-latex] (X) -- (2,0,0) node [left]  {$x$};
\draw[-latex] (Y) -- (0,2,0) node [right] {$y$};
\draw[-latex] (Z) -- (0,0,2) node [above] {$z$};
% equator
\begin{scope}[canvas is xy plane at z=0,blue]
  \draw                 (-45:1) arc (-45:135:1);
  \draw[loosely dashed] (315:1) arc (315:135:1);
\end{scope}
% meridian
\begin{scope}[canvas is xz plane at y=0,red]
  \draw[thick,my arrow={0.7}{4}] (-45:1) arc (-45: 90:1);
  \path[thick,my arrow={0.9}{2}] ( 90:1) arc ( 90:-45:1);
  \draw[thick,dashed]            (-90:1) arc (-90:-45:1);
  \draw                          ( 90:1) arc ( 90:135:1);
  \draw[dashed]                  (135:1) arc (135:270:1);
  
\end{scope}
% sphere
\draw (0,0,0) circle (1cm);
% dots
\foreach\z in {1,3}
  \fill[red] (0,0,2-\z) circle (0.5pt) node[below right] {$\z$};
\foreach\i in {X,Y}
  \fill (\i) circle (0.5pt);
\end{tikzpicture}
\end{document}



A: The best way I can imagine is the package tikz-3dplot. You can take a look at the documentation at the following link: tikz-3dplot_documenation.
You can also check this example which uses the same package for the figure produced: tikz-3dplot_example.

A: This is not a complete answer. You can try
\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{3dtools}
\begin{document}
    \begin{tikzpicture}[3d/install view={phi=110,theta=70},line cap=butt,
    line join=round,declare function={R=2.5;},c/.style={circle,fill,inner sep=1pt}] 
    \tikzset
    {axis/.style={blue,- latex}};
    \path
    (0,0,0) coordinate (O)
    (0,0,R)  coordinate (N)
    (0,0,-R)  coordinate (S);
    \path[save named path=sph,3d/screen coords] (O) circle[radius=R];
    \path pic{3d/circle on sphere={R=R,C={(O)}}};
    \path  pic{3d/circle on sphere={R=R,C={(O)},P={(O)}, n={(1,-9,0)}}}; 
    
    \path[save named path=ox] (0,0,0) -- (R+5,0,0) node[anchor=north east]{$x$};
    \path [save named path=oy] (0,0,0) -- (0,R+2,0) node[anchor=north west]{$y$};
    \path [save named path=oz] (0,0,0) -- (0,0,R+1.5) node[anchor=south]{$z$};
    \draw[3d/hidden] (S) -- (O);
        \tikzset{3d/ordered paths/.cd,ox/.style={blue,- latex},oy/.style={blue,- latex},oz/.style={blue,-latex}}
    \tikzset{3d/draw ordered paths={ox,oy,oz,sph}}
    \path foreach \p/\g in {O/-30,S/0,N/-30}
    {(\p)node[c]{}+(\g:2.5mm) node{$\p$}};
    \end{tikzpicture}
\end{document}


