Silicone or grout?

[Building_novice]

Hello,
Some tiling advice please. Just had my bathroom tiled, really unhappy, but now left with it, there are already cracks to the giant grout lines and where the floor meets the floor I’m concerned about water entering. AI tells me where the floor meets the walls (both being tiled) I should use silicone… there’s already grout in place. Google told me I should grout and then silicone over that… I wasn’t sure that would “stick” any advice on if I should use silicone? I’ve attached some photos. Thank you for your help!

 

[CountryFan]

If it’s just been done, why are you left with it? Get them back would be my answer. If you don’t want them back, as there’s already grout and doesn’t appear loose I would silicone seal over that.