keyboard problems

Hi, I bought a new keyboard.
The problems are the followings : in video games you would normally hold w key for running/walking, but my character keeps walking and stopping, basically like i said earlier, keys aren’t consistent
– the “i” and “k” keys aren’t working well, if i type “i” sometimes it doesn’t show up, sometimes i get two “i”s.
Please help me, how fix this problem?