Best to go straight to the source: the German Federal Ministry of the Interior, Building and Community.
You can find their offical press release -> here <- On violent crime:
In 2017, 188,946 cases of violent crime were recorded nationwide (2016: 193,542 cases), including 137,058 cases of dangerous and serious bodily harm (2016: 140,033). Compared to the previous year, violent crime was down slightly by 2.4%.
A brief summary of the stats can be downloaded near the top of the page.
The one table of statistics that is most relevant to the argument of immigrants or not can be found in that download and is given below:
As you can see, the number of suspects is down, down, down. Not just German suspects, but also non-German suspects (-22%).
But suspect is different to convicted offender, in the UK at least. Does suspect in Germany mean convicted offender? Dunno. So it may be possible that if unsolved crime had soared in Germany in 2017 then immigrants could be to blame IF the police were too scared of investigating fearing that the offender may be an immigrant.
So let's look at unsolved crimes.
2. Clear-up rate (CR)
The total clear-up rate is 57.1 %/55.7 % (2016: 56.2 %/54.0 %). The CR for murder and manslaughter is particularly high at 95.6%, as is the case with regard to crimes related to services, especially fare evasion 99.2 % and social benefits fraud 99.1 %.
The CR for theft offences with aggravated circumstances (e.g. bicycle theft, theft by burglary of a dwelling, theft of non-cash means of payment) is particularly low, at 15.1 %.
So, in summary, for these statistics:
1. crime in Germany in 2017 fell by 9.6% compared to 2016;
2. immigrants are not causing an increase in crime.
Ignore the media. I would urge you to read that little download of 2 pages linked to above.
II Crime Trends 2017
Section 1: number of crimes down by 9.6%
Section 5: increases in porn, drugs, economic crime and weapons, and decreases in shoplifting, pickpocketing and burglary
Section 7: decrease of 22% in non-German suspects.
But of course, they could be lying...