Hello Ulrike,

> 1. In the following document there is no space between the a and the y:
> 
> \documentclass{article}
> \begin{document}
> \noindent a\\y 
> 
> \bigskip  
> 
> a\par y
> \end{document}
> 
> It looks as if the lines have only the depth from their content. 

  I don't seem to see that (see attachment).  How did you generate the
format?  I used “luatex -ini pdflualatex.ini” where pdflualatex.ini
contains

	\pdfoutput1
	\input latex.ltx

> 2. I found here some code to use truetype and opentype fonts:
> http://luatex.bluwiki.com/go/Use_a_TrueType_font

  Oh, that ;-)  You really have to realize that these lines of code are
nothing more than an experiment I wrote one and a half year ago, and you
should be prepared to extend it if you want complete TrueType support
(not to mention OpenType features, which are absent altogether).  That
said, the problems should not be as bad as the ones you report below:

> a) I tested it with a latin modern font and arial and with both fonts
> all lines of a text are printed one above the other.
> of the lines have a height and a depth. 

  That's not what happens to me, you should really send a precise example.

> b) I also tried MnSymbol5.otf and there I get an error "invalid
> character". (I tried to get an "A"). With xetex the font works fine. 

  I can't confirm that.  I get the A all right (see attachment).  Again,
please send the precise example that fails.

	Arthur