Aug. 4, 1961 - In his recent speech to the nation on Berlin and the Communist challenge, President Kennedy said he would be glad to have suggestions on what to do. He is getting plenty of them. They range from offers to assassinate Premier Khrushchev to critiques of the President's grammar. Twenty thousand letters and telegrams have been received by the White House since the President's speech July 25. By far the most common suggestion is to cut Government spending. The individual who thought Mr. Khrushchev should be assassinated had no intention of shirking the job. He asked for "secret training to get into Russia and assassinate Khrushchev or as many as I can that are responsible for all of this world tension." It would be, he told the President, no worse than David slaying Goliath.