Ok.Thanks.I decided to concentrate on infect now and put out most of the wither creatures to leave the best in there like Lockjaw Snapper and Necroskitter .I'm not sure about Gift of the Deity since it is a good combination card with Quillspike and Devoted Druid (even without they are a quite big thread).I don't think I'll need Phyresis any more and Blight Sickle left for the same reason.Still left Tainted Strike for the opportunity to kill opponents with creatures of other opponents getting through.I'm yet not sure wich infect creatures to throw out and wich ones to leave in there so I don't lose this win condition. (Just cut out the ones without abilities, but am not sure for the rest)

I appreciate you help a lot since this deck still confuses me a bit.

If you do intend to win with infect damage, you'll need cards like Phyresis and Glistening Oil as well as proliferate sources like Plaguemaw Beast and Core Prowler . Good utility creatures shouldn't be avoided, who doesn't like Primeval Titan , and a Titan with infect is a scary thought.

Infect creatures in general are fragile beasts. They need pump spells and evasion to be at their best. Spells like Spread the Sickness and Ichor Rats are your friends, mass removal and reanimation will be your point men.

Or you could use The Mimeoplasm as a commander and play Infect Control, gives you access to Corrupted Conscience and that proliferate enchantment.

The Mimeoplasm is sweet because he can come in copying a creature in your graveyard, giving him infect, and picking a choice fatty to make him huge. Copying Phyrexian Crusader would be nice me thinks. Blue would give you access to Fate Transfer and Scarscale Ritual

Thanks for the suggestion.I'll put Phyresis back in to enchant creatures like Primeval Titan .The Mimeoplasm is a quite good idea but since I already have a deck with it I won't play it.And I think my actual Commander interacts quite good with the -1/-1 counters since he can kill creatures already having some.

With your commander, it seems like the perfect deck to run Pestilence and Pestilence Demon especially if you have a way to Untap him.