Hi sigmund1410,
for start recommend a few high quality general midi soundfonts from the Internet
for example:
CrisisGeneralMidi3.01.sf2 689MB
SGM-V2.01.sf2 237MB
SGM-180 v1.5.sf2 242MB
Arachno SoundFont 155MB
FluidR3 GM.SF2 148MB
unfortunately, renoise is slightly inaccurate when importing *.sf (Looppoints)
with Bass Midi VSTI you can easily compare and improve
https://forum.renoise.com/t/recommended-freeware-vst-plugins/22645
don’t know a good guitar simulation(s) (like guitar pro but not the sound)
recommend a cheap used no name fender/gibson clone e-guitar from ebay for 50 eu and a bit of exercise
TheBellows shows here impressively what is possible with renoise and effects
http://forum.renoise.com/index.php/topic/50423-songs-metal-example/?hl=metal
His other publications here, what he does with effects is also very instructive