Firstly to summarise the comments: figure environments may not appear in minipages. figure is a floating environment, but you want to place your graphics in a particular place. In principle, all you need is the \includegraphics, but as you notice, you do not get the vertical space you expect, so there may be other issues.
Let me run through your set-up to discuss several points.
Each minipage produces a box of typeset material, and these are placed essentially like individual characters you enter. In particular, blank lines between minipages will start new paragraphs and thus not stay on the same line. So many of the blank lines in your sample code need to be removed.
Next given that, many of the other constructs you use do not need to be encapsulated in a minipage. This applies in particular to the \hspace command. You can just write
\begin{minipage}...\end{minipage}\hspace{...}\begin{minipage}...\end{minipage}
as you would write
a\hspace{...}b
to get horizontal spacing between objects.
Similarly, an image can be included directly; the \includegraphics command produces another box of typeset material that is again placed much like a character. You can use \raisebox to adjust its vertical placing if necessary.
On the other hand, if you are using figure because you wanted to have a caption and figure number available, then using a minipage to include this and the caption would be appropriate. You can then use the caption package, which as \captionof command:
\begin{minipage}[t]{0.4\linewidth}
\vspace{-2ex}
\includegraphics{...}
\captionof{figure}{Caption}
\end{minipage}
Note the use of a \vspace before the graphics; without it the first line of the minipage is very high, but the [t] option aligns on the baseline of the first line of the minipage so the image sticks up. -2ex is essentially the height of a capital letter, and will place the image so its top edge aligns with those. See Aligning image and text on top, with minipages for further discussion of such alignment of images in minipages.
Here is a modified version of your example putting these things together (irrelevant packages have been stripped out):

\documentclass[11pt,a4paper]{article}
\usepackage{graphicx,caption}
\usepackage[top=2cm, bottom=3cm,right=1cm, left=1cm, headsep=26pt]{geometry}
\usepackage{helvet}
\renewcommand{\familydefault}{\sfdefault}
\begin{document}
\begin{minipage}[t]{.98\linewidth}
\begin{minipage}[t]{0.33\linewidth}
\setlength{\parindent}{1em}
Some text over several lines.
Some text over several lines.
Some text over several lines in a new paragraph.
\end{minipage}
\hspace{4em plus 1fill}
\begin{minipage}[t]{0.2\linewidth}
\setlength{\parindent}{1em}
Some text over several lines.
Some text over several lines.
Some text over several lines in a new paragraph.
\end{minipage}
\quad
\begin{minipage}[t]{0.2\linewidth}
\vspace{-2ex}
\includegraphics[width=1.0\linewidth]{example-image-a}
\captionof{figure}{Caption}
\end{minipage}
\end{minipage}
\end{document}
I have used \quad to space off the image minipage from the that for text to the left. This is equivalent to \hspace{1em}. For the space between the first two blocks, I used \hspace{4em plus 1fill}, this is a minimum of four quads but stretches to fill out the available room. The effect here is that your first minipage is flushleft, and the last pair is pushed flushright.
In the minipages, I set the paragraph indents; they are zero by default.
Note that minipage is quite a complex construct. It is appropriate if the material is long and includes several paragraphs. If it is just a single paragraph then \parbox is a better choice. See \parbox vs. minipage: Differences in applicability for a discussion.
figurewithin aminipage. Remove the surroundingminipage. – Stefan Kottwitz Jul 17 '13 at 06:16\begin{figure}[h!]and\end{figure}. Please include only\includegraphics[...]{...}. – Jagath Jul 17 '13 at 06:17\includegraphicsin afigureenvironment. TeX sees\includegraphics[...]{...}just like a big letter. – egreg Jul 17 '13 at 06:25caption(\usepackage{caption}) and use\captionof{figure}{your caption}to get caption outsidefigureenvironment.\captionofcommand is also provided bycapt-ofpackage – Jul 17 '13 at 06:42minipageswith aparboxcommand. It is more robust and hence may make life a little easier. Minipages are good if you want to use specific properties likempfootnotes– Martin - マーチン Jul 17 '13 at 08:50minipagebut\begin{figure}environment and the! LaTeX Error: Not in outer par mode.error was due to a missing\end{figure}. You should look through your document and see if something like\end{minipage}is not missing. – esmitex Aug 29 '13 at 20:42