Hello Neshi,
Thank you for posting issue, before we start, Please provide your website link so that we can analyze your issue.
for banner slider, you need to place atleast 2 post items from go to customizer > slider section
to display arrow and bubble.
for testimonial slider, you need to place atlease 3 post form customizer> home page settings > testimonail section.
for other slider also please check you have provide sufficient items.
if you have provided items please check if you have installed third party plugins, please check by disabling installed plugins.
Best Regards,
prosys theme