@vanvugt Thank you for your answer.
I tried the kernel versions 5.0.0-13 and 4.3.0-04 as well. For the first one, the same problem occured (sound only after a fresh boot) and the second one couldn't be installed correctly because of missing libraries (a boot was possible, but e.g. the mouse pointer was not moving).
I have already tried to reconfigure pulseaudio, to force alsa-audio to reload (it does reload but doesn't change anything).

Here is my output of aplay:
$ aplay -L
default
    Playback/recording through the PulseAudio sound server
null
    Discard all samples (playback) or generate zero samples (capture)
jack
    JACK Audio Connection Kit
pulse
    PulseAudio Sound Server
sysdefault:CARD=PCH
    HDA Intel PCH, ALC236 Analog
    Default Audio Device
front:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    Front speakers
surround21:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    4.0 Surround output to Front and Rear speakers
surround41:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
hdmi:CARD=PCH,DEV=0
    HDA Intel PCH, HDMI 0
    HDMI Audio Output
hdmi:CARD=PCH,DEV=1
    HDA Intel PCH, HDMI 1
    HDMI Audio Output
hdmi:CARD=PCH,DEV=2
    HDA Intel PCH, HDMI 2
    HDMI Audio Output
hdmi:CARD=PCH,DEV=3
    HDA Intel PCH, HDMI 3
    HDMI Audio Output
hdmi:CARD=PCH,DEV=4
    HDA Intel PCH, HDMI 4
    HDMI Audio Output
dmix:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    Direct sample mixing device
dmix:CARD=PCH,DEV=3
    HDA Intel PCH, HDMI 0
    Direct sample mixing device
dmix:CARD=PCH,DEV=7
    HDA Intel PCH, HDMI 1
    Direct sample mixing device
dmix:CARD=PCH,DEV=8
    HDA Intel PCH, HDMI 2
    Direct sample mixing device
dmix:CARD=PCH,DEV=9
    HDA Intel PCH, HDMI 3
    Direct sample mixing device
dmix:CARD=PCH,DEV=10
    HDA Intel PCH, HDMI 4
    Direct sample mixing device
dsnoop:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    Direct sample snooping device
dsnoop:CARD=PCH,DEV=3
    HDA Intel PCH, HDMI 0
    Direct sample snooping device
dsnoop:CARD=PCH,DEV=7
    HDA Intel PCH, HDMI 1
    Direct sample snooping device
dsnoop:CARD=PCH,DEV=8
    HDA Intel PCH, HDMI 2
    Direct sample snooping device
dsnoop:CARD=PCH,DEV=9
    HDA Intel PCH, HDMI 3
    Direct sample snooping device
dsnoop:CARD=PCH,DEV=10
    HDA Intel PCH, HDMI 4
    Direct sample snooping device
hw:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    Direct hardware device without any conversions
hw:CARD=PCH,DEV=3
    HDA Intel PCH, HDMI 0
    Direct hardware device without any conversions
hw:CARD=PCH,DEV=7
    HDA Intel PCH, HDMI 1
    Direct hardware device without any conversions
hw:CARD=PCH,DEV=8
    HDA Intel PCH, HDMI 2
    Direct hardware device without any conversions
hw:CARD=PCH,DEV=9
    HDA Intel PCH, HDMI 3
    Direct hardware device without any conversions
hw:CARD=PCH,DEV=10
    HDA Intel PCH, HDMI 4
    Direct hardware device without any conversions
plughw:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    Hardware device with all software conversions
plughw:CARD=PCH,DEV=3
    HDA Intel PCH, HDMI 0
    Hardware device with all software conversions
plughw:CARD=PCH,DEV=7
    HDA Intel PCH, HDMI 1
    Hardware device with all software conversions
plughw:CARD=PCH,DEV=8
    HDA Intel PCH, HDMI 2
    Hardware device with all software conversions
plughw:CARD=PCH,DEV=9
    HDA Intel PCH, HDMI 3
    Hardware device with all software conversions
plughw:CARD=PCH,DEV=10
    HDA Intel PCH, HDMI 4
    Hardware device with all software conversions
usbstream:CARD=PCH
    HDA Intel PCH
    USB Stream Output